Professor, Claudia Ratti

eynt toujours été quelqu9un de très urieuxD les sienes nturelles me sont rpideE ment pprues omme une disipline de hoix u ours de m solritéF in prtiulierD les sienes physiques ont été un déli dès l (n du ollègeD à l mention de l9existene des tomes et de l struture mirosopique de l mtièreF ves quelques ours de physique nuléire et de reltivité restreinte que j9i pu suivre u lyée ont lors été une vrie révéltionD et m9ont permis d9entrer à l9niversité en ynt pour ojetif de réliser un jourD si possileD un dotort en physique des prtiulesF ge mnusrit ttestnt insi de et omplissementD je tiens vnt toute hose à remerier en quelques pges toutes les personnes qui m9ont permis d9ller u out de ette ventureF te ne vis ien évidemE ment ps pouvoir nommer une pr une toutes es personnesD et j9espère don que elles et eux que j9uris omisFes de iter nomintivement ne m9en tiendront ps rigueurF te ne vous oulie ps 3 À noter queD ertines personnes que je tiens à remerier ne prlnt ps frnçisD je rédigeri les pssges les onernnt en nglisF te souhiteris tout d9ord ommener pr remerier les di'érents memres de mon juryF por epting to e reviewers of my thesis mnusriptD s would like to thnk foris omá²ik nd wgdlen hjordjeviD espeilly when onsidering the struggle s hd to respet the dedlinesF hnks for your ptiene nd omprehensionD s well s for ll the useful feedks you hve given to meY s truly ppreited nd vlued themF he l même fçonD je tiens à remerier tenEves yllitrultD pour les longues onverstions très inE téressntes à propos de mon trvilD et wrlène xhrgng pour m9voir églement donné de nomreuses pistes de ré)exionD en plus d9voir été une exellente professeure durnt mon wsterF t9dresse des remeriements tout prtiuliers à rh orteoeufEroussisD qui est en quelque sorte m 4mrrine4 de professionD l personne qui m9 initié à l reherhe en physique des hutes énergiesF weri pour toute l9inspirtion que tu m9s donnée u trvers des disussions que nous vons pu voirD mis ussi simplement de pr ton proursF s lso owe unspekle thnks to gludi ttiD who did not only mnge to (nd the time to ttend my defense despite the distne nd the time shiftD ut lso epted erlier in my hh to e prt of my followEup ommitteeF wost of llD thnk you for o'ering me postdotorl position with you in suh gret environment like roustonD nd for eing suh nie nd inspiring dvisorD ollortor nd friendF qrzie mille per tutto 3 hespite not eing prt of my juryD s lso wnted to thnk vudmil wE linin for eing the other memer of my followEup ommitteeD nd hving shown interest in my workF sl est évident que ette expériene n9urit jmis pu voir lieu sns l on(ne que m9 ordée ulusD en me proposnt ette thèse sous s diretion vnt même que je n9entme m deuxième nnée de wsterF weri pour t onstnte onne humeurD et pour t rétivitéF gette thèse ynt été mrquée pr l pndémie de govidEIWD il m9 été d9une grnde ide de pouvoir ompter sur nos éhnges mlgré les on(nements suessifsF te I eguxyvihqiwix G iwigsiwix te suis églement reonnissnt pour toute l lierté que tu m9s ordée durnt es trois nnées et demiD en me lissnt enseigner et prtiiper à de nomreuses onférenes notmmentD tout en shnt me guider ve sgesse dns mon projet de reherheF ge svnt mélnge m9 pporté énormément en tnt que herheurD et très ertinement été déisif pour le déut de m rrièreF te n9uris honnêtement ps pu imginer de meilleur endrement pour réliser mon dotortF weri d9voir prtgé ve moi une prtie de ton inroyle expertise et de tes onnissnes dns le domine de l physique des ions lourdsD et j9espère que notre ollortion ontinuer ussi frutueusement que possile 3 v9environnement de trvil est églement un élément lé pour le on déroulé d9un doE tortD et j9i pu ompter pour el sur le dre idél du lortoire utehF te remerie pour ommener l9ensemle du groupe du héorie dns lequel j9i e'etué ette thèseF ge fut un réel plisir de ôtoyerD en tnt que désormis ollèguesD elles et eux qui furent pour l pluprt mes professeurFeFs uprvntF weri à hierryD pour voir ssuré un rôle essentiel à l tête du groupe durnt l qusiEtotlité de mon dotortD en plus d9voir été un interlouteur privilégié de prt s position de responsle du wster peF ne utre pensée prtiulière à quyD pour voir été un exellent endrnt lors de mon tout premier stge de reherheD insi qu9un professeur pssionné et pssionnntF te retiens églement les ons moments pssés à intEtutEdeElEwer en ompgnie de téphne F et prnçoisD e qui notmment permis d9mener l pétnque à l ghntrerieF in(nD je tiens à remerier olEfernrd pour voir ppuyé ve utnt de sympthie mes nE didtures de postdo à l9étrngerD et pour m9voir soutenu et rssuré qunt à l9idée de vivre une telle expériene ussi loin de m ville ntleF in tnt que résident temporire du ouloir rPHHD j9i eu l hne de ôtoyer quotidiennement l diretion insi que toute l9équipe dministrtive du lortoireF weri don à qinésD olEfernrd @à nouveuAD sselle et tenEvu pour voir formé une équipe de diretion de hoD du moins de mon point de vueF n grnd meri à éroD éverineD werrylD téphnieD ndrineD slineD enneD njD endres et xdège pour votre trvil indispensle u on fontionnement du lortoireD et pour les onjours sourints du mtin 3 t9i ien sûr volontirement omis de iter ophie et prhD de pr l ple spéile qu9elles oupent dns e groupeF weri à vous deux pour voir été des prtenires de dminton inftigles @ou presqueAD pour toutes les disussionsD puses fés et utres tivités extrEprofessionnelles en votre ompgnieF te remerie ien sûr tout l9ensemle du lortoire pour voir ontriué à me fire sentir omme hez moi sur mon lieu de trvilD et voir ontriué à en fire un environnement si stimulntF weri prtiulièrement à hmienD qillesD wrusD topoD tenEwihelD uhlilD ierrikD irwn wFD wxime qFD wrieD quillume fFD ernudD ihrd et vilin entre utres @et je dois réger ii l liste des noms si je ne veux ps me retrouver à iter l9ensemle du personnelFFFAF ge qui rendu ette expériene si uniqueD 9est ussi ien sûr l ompgnie es utres dotorntFeFs ve qui j9i prtgé es nnées à utehF weri tout d9ord ux 4nE ienFneFs4D à ommener pr le duo de ho qriel @ei3A et hvid pzouD olndD yphé et ghrdmouD mis ussi wnuD hvid rFD ghloéD enthony et irwnnD pour voir su nous ueillir et nous intégrer ussi filement dns e groupeF wrysiD thnk you very muh for hving een wonderful supervisor during my (rst months thereD nd for eoming wonderful friend tooF fien évidemmentD mes mrdes de promotions sont les premières personnes qui me viennent à l9espritD e 4ru4 ynt été si spéil pour moi de prt l onne mine qui régnit entre nousF weri énormément à erthur notre prisien préféréD inent @mlgré son rrivée trdiveAD it m mrde de krokéD m sist gludi et qoiregré l9homme en hussettes qui m9 ompgné dns mon exil P eguxyvihqiwix G iwigsiwix mériinF wention spéile à wihelD notre fritish guy who 4does not tlk like this34D mon prtenire de ureu depuis notre rrivée à utehD pour les nomreuses disusE sions sur tnt de sujets plus intéressnts les uns que les utresD et toutes les fois où tu s pris le temps de m9ider ve tnt de persévérneF ve oeur de e groupeD eux ve qui j9imis désigner le qutuor que nous formions sous le nom de 4R fntstiques4D e sont mes mrdes de wster homsD wxime et itorF n immense meri pour toutX les 4rello sunshine4D les fmeuses puses thé dns le slonD tous les délires et ons moments prtgés ensemleF g9est ette lhimie si prtiulière entre nous qui nous permis de trverser toutes es épreuves pourtnt ps si évidentes ensemleD et je suis heureux d9voir pu le fire en ompgnie de personnes ussi inroyles que vousF weri ussi à mes utres ollègues de ureu henys et whoehD pour voir prtgé mon quotidien et toutes es petites hoses qui ont réé e lien prtiulier ve vousF he mêmeD je remerie mes voisins de ureu téphneD xthn et imonnD ve qui j9i pssé euoup de temps à disuterD ien que rrement à propos du trvilF te n9oulie ps non plus xdiy et rnn Y meri d9être venues pporter un peu de sng nouveuD de joie et de onne humeur dns notre groupe près es interminles on(nementsF weri en(n à tous eux qui sont venus ompléter les rngs plus trdivementD notmment véonrdD xioD tohnD elexnderD itor FD oie et pélixF te tenis à remerier églement toutes les personnes de pssgeD omme entoine FD quillume pFD notre hôte de ureu pendnt quelques mois ve qui j9i ppréié d9voir eu utnt de disussions sur nos projets futursD ou ien enore tous les stgiires que j9i pu ôtoyerF fien sûrD je remerie en prtiulier les stgiires que j9i personnellement endrésD pour tout e qu9ils et elles m9ont pporté en éhnge de e que j9i pu leur pprendreF weri don à qriel FD vierD Émilie wFD wme l présidente Émilie fF et ghloé qui visilement tellement ppréié de trviller sur iy qu9elle est revenue une deuxième fois 3 n énorme meri à exelD r je n9uris ps pu espérer mieux (nir m thèse qu9en endrnt en stge un étudint ussi utonomeD perspieD et prEdessus tout un miF t9i doré l9expériene de pouvoir enseigner à l9niversité durnt les deux premières nnées m thèseD et 9est en grnde prtie grâe ux très ons ontts que j9i pu voir ve les étudintFeFsD que je remerie don à leur tourF t9espère voir été à l huteurD en vous rendnt l9pprentissge de l physique un peu plus fileD et en y ynt donné du sensD en prtiulier durnt les périodes de ours à distne dues ux di'érents on(neE mentsF re que j9i ussi été un étudint vnt d9en rriver làD j9i une pensée pour tous les enseignntFeFs qui m9ont permis d9ppréhender l physique u trvers de mon prours universitireF te remerie notmment hierry et tulienD les responsles du wster pe et du prours à ette époqueD mis ussi toute l9équipe pédgogique pour voir ssuré un enseignement que j9i grndement ppréiéF in(nD je remerie spéilement ylivier velD direteur du déprtement de hysiqueD pour m9voir fit on(ne en me proposnt des tâhes d9enseignementD pour voir été un professeur de physique de prtiE ule et d9stroprtiules ussi pssionnntF weri de nous voir motivéFeFs et soutenuFeFs dns l rétion de v9essoition des itudintFeFs de hysique de xntes @veitoxAD quiD je l9espèreD ssurer ussi longtemps que possile s mission u sein de l9niversité de xntesF t9en pro(te insi pour remerier de même toutes les personnes qui ont pris prt et ontriué à l vie de ette ssoitionF ges nnées pssées à l9niversité de xntes m9ont permisesD uEdelà d9évoluer dns un milieu qui m9 tnt pportéD de fire de superes renontresF ves premières personnes que je souhite remerier sont évidemment wrgotD ilieD eddy FD uentin venouvel et Q eguxyvihqiwix G iwigsiwix itorD pour voir été ussi présentsD e enore ujourd9hui mlgré l distneD et pour être des mis ussi géniux et (dèlesF weri prtiulièrement à itorD pour voir été mon inftigle ompgnon de route durnt es IH dernières nnéesD ve qui j9i pu tnt prtger et sur qui j9i toujours pu ompterF t9i le sentiment que vous vez touFteFs ontriué à fire de moi l personne que je suis ujourd9huiD et j9espère pouvoir ontinuer à vous ompter dns mes plus prohes miFeFs ussi longtemps que possileF fien sûrD je remerie ussi toute m promotion de wsterD et notmment uentin vesigneD wthildeD eddy hFD insi que ierre le ipou dont l venue à m soutenne m9 sinèrement touhéF n grnd meri églement ux 4pux xntis4D pour voir rempli notre dernière nnée de viene d9utnt de si ons momentsD insi qu9à go et ersène durnt notre nnée de viene PF weri en(n à tous les utres mrdes qui ont ontriué à rendre es nnées de viene ussi gréles à vivreF fien qu9il soit di0ile d9y mettre de simples motsD je tiens à exprimer l9immense grtitude que je ressens pour l personne qui oupé une ple si spéile durnt les U dernières nnées et demi de m vieF weri in(niment d9voir grémenté toutes es nnées pssées ensemle de moments de joie et de onheurF weri pour le soutien que tu m9s pporté u quotidienD dns tous les projets que j9i entreprisD et pour l9in)uene onsidérlement positive que tu s eue dns m vieF weri d9voir été à l9éouteD d9voir été présente dns les moments di0ilesD et d9voir su trouver les mots justes pour me pousser vers l9vnt lorsque 9étit néessireD tout en m9empêhnt de me noyer dns le trvil lorsque je me sentis dépsséF te ne seris sûrement ps sorti ussi grndi de toutes es expérienes sns toi à mes ôtésD et je te seri toujours reonnissnt pour elF te remerie de même sinèrement m elleEfmille d9lors pour voir ru en moiD et pour m9voir o'ert tnt de prenthèses de onne humeur et de ons momentsF our (nirD je remerie vnt tout mes prentsD du fond du oeurD pour m9voir toujours poussé à donner le meilleur de moiEmêmeD et surtout pour m9voir toujours lissé l lierté de suivre l voie que je désiris emprunterD sns jmis voir douté de moiF weri d9voir fit tout votre possile pour que je puisse réliser e que je souhitis fire dns l vieD d9voir onsidéré que le ienEêtre et le onheur de vos enfnts étit une prioritéD et que el pssit vnt tout pr les ider à omplir leurs rêvesD qund ien même el signi(it nous voir prendre des voies qui vous étient omplètement inonnuesF weri à m petite soeur de m9voir supporté depuis toujoursD dns le sens positif omme négtif du termeD il fut l9dmettreF weri ussi et surtout pour voir étéD ien que m detteD une réelle soure d9inspirtion pour ton ourge et t détermintionF weri à mon petit frère pour m9voir idé à sortir de si nomreuses fois de m ulleD et pour tout e qu9on pu prtger ensemle mlgré notre di'érene d9âgeF te remerie ussi l9ensemle de m grnde fmille pour m9voir toujours énormément soutenuD pour voir été motivnts et ienveillntsD mis ussi ompréhensifs lorsque mon trvil m9oligeit mlheureusement à mnquer des élértions ve vousF te suis heureux et (er d9être le premier hrF de ette fmilleD et 9est en grnde prtie grâe à vous tous que j9i pu omplir elF ne mention spéile à mon onle et m tnte qui ont epté de se hrger de l préprtion de mon pot de thèse X je n9uris ps pu espérer mieux (nir m thèse utrementD meri euoupF in(nD un énorme meri à mes grndsEprents pour tout e qu9ils m9ont pporté dns l vieD toutes les vleurs qu9ils m9ont trnsmisesD et en prtiulier à mes grndsE prents mternels pour voir été présents le jour de m soutenneD ien qu9ignornt tout de mon trvil et ne prlnt ps un mot d9nglisF te termine es remeriements ve quelques mots pour mon grndEpère pternelD renriD qui nous mlheureusement quitté vnt de me voir omplir tout elF re que tu s été un modèle de sgesse toute m vieD je te dédie ette thèse piF INTRODUCTION row does mtter tke formc ht re weD the world surrounding usD nd even the whole niverseD fundmentlly mde ofc hese questionsD whih nyone might hve sked themselves t some pointD re the ultimte resons motivting the work presented in this thesisF hnks to the inredile knowledge quired from enturies of progress in siene nd tehnologyD we know tht ordinry mtter of whih we re omposed is mde of tomsD whose properties nd ehviours re now studied in tomi physis nd hemE istryF iven more fundmentllyD prtile physis fouses on how the tom9s omponentsD i.e. eletronsD nuleons nd the qurks nd gluons inside themD intert t suh tiny slesF wy reserh tkes ple in this ontextD nd is more prtiulrly relted to the theory used to desrie the strong intertionX the quntum hromodynmis @ghAF e (rst importnt property of this theory is the olour on(nementD the ft tht qurks nd gluonsD whih rry olour hrge proper to this intertionD re lwys on(ned in omposite prtiles lled hdronsF yne diret onsequene is tht they n only e proedD elow the femtometer sleD in highEenergy ollisions performed in powerful E elertors suh sD mong othersD the gints vrg or rsgF elmost hlf entury goD while gh ws just estlishedD some physiists suggested tht there might exist stte of mtter where qurks nd gluons re deon(nedD lled the qurkEgluon plsm @qAF he oservtion of this new stte of mtterD expeted to ompose the ore of neutron strs nd formerly the erly niverseD hs een formlly nnouned in the (rst hlf of the PHHH9s dede y severl experimentl ollortionsD fter hving gthered severl piees of evideneF he study of the q is hieved vi reltivisti hevyEion ollisionsD whih llows to reh the high temperture nd density required for its formtionF roweverD olleting informtion out it is hllengingX eE use of its very short lifetime @∼ 10 -23 sAD the q droplet reted in suh ollisions ools down nd returns to the hdroni phse efore rehing the detetorsF reneD it is only possile to ess its properties indiretlyD vi the signtures imprinted in the (nlEstte hdrons originting from its freezeEoutF e spei( topi of interest in tht (eld is the hrteristion of the phse digrm of nuler mtterD i.e. determining under whih onditions preisely q n e reE tedD where re the phse trnsitions to hdroni gsD nd wht is the nture of these trnsitionsF xowdysD the thermodynmis of this fundmentl mtter nnot e deterE mined ompletely from the (rst priniples of the theoryD thoughF his is due to nother importnt property of ghD the ft tht its oupling onstnt depends on the energy sleD nd so the strength of the strong intertion etween qurksF reneD perturtive lultions n only e hieved t high energyD nd it is impossile to desrie the trnE U sxyhgsyx sition from q to hdron phse nlytillyF here exists however one pprohD onsisting of disretising speEtime in lttie nd lled lttie quntum hromodyE nmis @lghAD whih llow to resolve it nonEperturtively vi numeril simultionsD ut only t zero or limited ryoni densityF hese simultions enled to predit rossover trnsition etween the q nd the hdron gs in this regionD whih is the only prt of the phse digrm known with ertitude so frF xonethelessD severl other models predit the existene of 1 st order phse trnsition t (nite ryoni densityD tht involves the existene of ritil endpoint @giA due to the rossover trnsition t low densityF wy work will fous on the serh for this gi vi the study of )ututions of onE served hrges @ryoni numerD strngeness nd eletri hrgeAD whih re expeted to diverge in its viinityD nd so indite its lotionF hey re qunti(ed theoretilly y the soElled suseptiilitiesD lulted with lgh or the sttistil therml rdron esonne qs @rqA modelD nd evluted experimentlly through moments of the netEmultipliity distriutions of hdrons rrying the hrges of interestF hese mesureE ments re notly hieved y the e experiment in the frme of the Beam Energy Scan @fiA progrmD whose gol is to serh for experimentl signtures of the gi y hieving euEeu ollisions t mny energiesF fy doing soD they rete di'erent systems desriing severl trjetories whih proe lrge region of the phse digrmD hoping to see ny lue hinting for the presene of giF gonsideringD howeverD the fundmentl di'erenes etween theoretil idelised system t equiliriumD nd the highly dynmiE l system reted in hevyEion ollisionsD it is primordil to understnd the experimentl limittions towrd these )utution oservles to relte them properly to the theoryF uh investigtions re only possile y using phenomenologil pprohes to simulte ollisionsD in prtiulr thnks to event genertorsD whih re the most relisti tools developed for this purposeF reneD the (rst ojetive of my study is to quntify the impt of hdroni sdesD the suessive reEintertions etween formed hdrons t the lte stge of the ollisionsD on the 2 nd order umulnts of netEpionsD netEkons nd netEprotonsD y using suh simultionsF he underlying motivtion is to see how these proxies mesured y eD supposedly relted to the )ututions of onserved hrgesD re impted y proesses whih re not relted to ny ritil ehviour of the nuler mtterF enother ojetive is to ompre these oservles to some 4enhned4 proxiesD expeted to etter reprodue the theoretil suseptiilities s proposed fter study using rq model lultionsF foth of them ould (nlly e ompred to the umuE lnts of the ext orresponding onserved hrgesD s event genertors enle to ess ll the hdrons reted in the simulted eventsD to see how e'etive proxies they re trulyF o this endD s used the iy event genertorD whih is sed on unique theory for initil intertions mixing multiple sttering pproh nd perturtive ghD nd whih fetures reltivisti visous hydrodynmi evolution of the ulk mtter reted in the simulted ollisionsF wy study ws led during the preprtion of new versionD iy RD to e pulily relesed soonF husD in order to improve the usility of iyD s dpted it in prllel to mke it omptile with the ivet softwreF o go even furtherD s even integrted this tool whih o'ers n utomtistion of the omprison etween event genertor simultions nd experimentl dtD into the iy nlysis frmeworkD so tht developers ould lso ene(t from itF por the energy rnge of the fi progrmD s lso wrote mny nlyses in the iy frmework itselfD for the ones not ville in ivetD to ompre its results to experimentl dtF husD it llows testing the prmetristion vlidity efore the puli releseD nd ensures tht the simulted events used for my min study exhiit good desription of wht we oserve experimentllyF V sxyhgsyx sn the following mnusriptD s will therefore introdue rie)y in ghpter I the generl ontext of the tndrd wodelD with spei( fous on ghF ghpter P will e dedited to the physis of hevyEion ollisions nd the study of the qD to introdue the serh of the ritil point in the phse digrm of nuler mtter s well s the tools to used to hieve itF s will end it with presenttion of the two min pulitions whih inspired my workD followed y the detiled motivtions of my studyF sn the ghpter QD s will present iy nd outline the min ojetives of my thesis s onlusionF pinllyD ghpter R will ontin the desription of the tehnil work relted to iy nd ivetD nd ghpter S the results of my study on the 2 nd ine entiquityD sientists hve elorted theories nd experiments to explin wht mtter is mde ofF he onept of tomsD s tiny indivisile elementry piees omE posing everythingD hs een proposed y enient qreek philosophers hemoritus nd veuippus during the 6 th entury fgF roweverD the ide ws only lrgely epted in the sienti( ommunity y the end of the IW th enturyD thnks to the work of e.g. tohn hltonD emedeo evogdro or tmes glerk wxwellF et the dwn of the PH th enturyD the disovery of eletrons y toseph tF homson ID quikly followed y the one of the tomi nuleus y irnest utherfordD rns qeiger nd irnest wrsden PD QD proved tht toms were (nlly not the most elementry piees of mtterF efter the pioneerE ing work of wx lnk nd elert iinstein towrds the intertion etween light nd toms RD SD xiels fohr developed quntum tomi model pulished in IWIQ T!VF his progress ledD during wht is onsidered to e the golden ge of modern physisD to the development of quntum mehnisD fundmentl theory used to desrie how prtiles ehve nd intert with eh others elow the nnometre sleF he min priniples of this theoryD s well s the proper formlism to desrie itD were minly estlished during the IWPHs y numerous physiists like vouis de froglieD erner reisenergD wx fornD irwin hrödinger or ul hirD to nme just few fmous onesF he IWQHs dede sw further progress on the understnding of the fundmentl inE tertionsF sn n ttempt to explin rdiotive βEdeyD the ses of wek intertion were set y olfgng uli who postulted the existene of the neutrino WD nd y inrio permiD who inorported this new prtile into formultion of ontt inE tertion to desrie the proess responsile for this dey IHF tmes ghdwik lso rought to light the existene of the neutron IID whih eventully led to the disovery of the neutronEindued nuler (ssion y ytto rhnD pritz trssmnn nd vise weitner IPD IQF st opened gte to powerful new soure of energyD whih ws t (rst sdly fmous for its militry pplitionD ut ws lso exploited fterwrds for ivil purposes nd therefore providing eletriity for millions of peopleF he politioEeonomil ontext of the postEorld r ss er pushed mny ountries to invest in fundmentl reserhF husD mny emerin lortories quikly develE oped lrge experimentl omplexes thnks to the legy of the wnhttn rojetD while the European Organization for Nuclear ResearchD or 4Conseil Européen pour la Recherche Nucléaire4 @gixA ws reted in IWSR in qenevF sn prtiulrD the importnt progress on elertor physis nd tehnologies llowed to hieve prtile ollisions t greter nd greter energiesD proing thus smller nd smller length slesF prom there ws orn the (eld of modern prtile physisD whih hs developed until now into ommunity of severl thousnds of tive reserhers ll round the worldF hespite the signi(nt dvnes in our knowledge of mtter nd fundmentl intertionsD our motivtions remin the smeX to understnd the lws tht govern our universe t mirosopil levelF ine the work presented in this thesis is prt of tht dynmiD s will introdue in setion IFI of this hpter the rod lines of the tndrd wodel of prtile physisD the most omplete nd dvned theory desriing mtter t suh sle up to dteD lthough known to e limitedF s will then desrie with little it more detils in setion IFP the history nd prinipl spets of ghD the theory desriing strong intertionD whih is the min kground of my workF his will open the wy to hpter PD where s will depit more preisely the ontext of the reserh presented in this thesisX the study of qurkEgluon plsm in reltivisti hevyEion ollisionsF IP IFIF ri exheh wyhiv yp esgvi rsg 1.1 The Standard Model of particle physics he tndrd wodel of prtiles physisD often simply referred to s the tndrd wodel @wAD desries how elementry prtiles intert with eh other vi eletromgE netiD wek nd strong intertionsD in the frmework of quntum (eld theory @pA sed on (3) ⊗ (2) ⊗ (1) guge symmetry IRF st o'ers solid theoretil desripE tion of those three fundmentl foresD from whih severl preditions hve een vlidted y posterior mesurements nd none ever formlly refuted so frF xeverthelessD the ft tht the w hs never een formlly ontrdited experimentlly does not men it is )wlessF reneD fter giving short desription of its key ingredientsD s will rie)y disE uss its limitsD nd mention some theories estlished to desrie physis eyond the tndrd wodel @fwAF 1.1.1 General description he di'erent elementry prtiles omposing the w re listed in pigure IFIF he twelve prtiles omposing mtterD on the left pnelD re the soElled fermionsD generlly lssi(ed in three genertions fter their mss hierrhy @their ntiprtilesD whih just hve opposite eletri hrgeD re not displyed hereAF hese fermionsD rrying spin vlue of 1/2D re themselves divided into two groups lled qurks nd leptonsF yn the right pnel re shown the osonsD prtiles rrying n integer spin vlueD mong whih the four guge osons re vetors of the fundmentl intertionsF he eletromgneti @iwA intertionD the elderly known of the three desried y the wD is desried in this frmework y the soElled quntum eletrodynmis @ihAF st rules how ll eletrilly hrged prtiles intert with photonsD pitured y the γ symolF he Z 0 nd W ± osons re vetors of the wek intertionD respetively responsile for the elsti intertion of neutrinos with other fermions vi neutrl urrents ITD nd for )vourEhnging retionsF he hrged W osons ouple with the two di'erent leptoni speies of sme genertion @e.g. eletron e nd eletroni neutrino ν e AD IQ grei IF esgvi rsgX pyw riy y iiswix s well s qurks of di'erent )voursD eing therefore responsile for rdiotive βEdey nd dey of hevyE)voured hdrons @i.e. ontining qurks of P nd nd Q rd genertionAF por instneD in the βEdey of rdiotive nuleus whih sees one of his neutrons n trnsformed into proton pD the tul underlying proess involving the )vour hnge of qurk isX

ud d n W -→ e -+νe --------→ ud u p + e -+ νe .
@IFIFIA he mixing prmeters etween qurks )vours re given in unitry mtrix lled gioEuoyshiEwskw @guwA mtrixD nmed fter the sientists who elorted it IUD IVF prom this mtrixD one n dedue the trnsition proility from one qurk of )vour i to nother of )vour jD y squring the orresponding element V ij Y heneD the unitrity of the guw mtrix n e esily tested y heking if j |V ij | 2 = 1 for ny given iF he prmeters of the mtrix hve een experimentlly determined with the following upEtoEdte vlues IRX @IFIFPA he iw nd wek intertions re in ft two fes of the sme intertionD the eleE trowek @iA intertion IW!PIF felow given energy sleD they dissoite from eh other due to the inglert!frout!riggs!qurlnik!rgen!uile mehnism PP!PRF o mke it simpleD due to the reking of wek isospin symmetryD this mehnism provides mss to the W nd Z osons vi intertion with the soElled riggs (eldD intertion medited y the ssoited riggs osonF elthough with di'erent mehnismD fermions lso quire mss y interting with the riggs (eldD while photons remin msslessF he lst element of pigure IFI yet not disussed is the gluonD vetor of the strong intertionD whih is the third fundmentl intertion inluded in the w desriptionF grrying spei( hrge lled 4olour4D the gluon only interts with itself nd with qurksD whih hve in ddition the spei(ity to e the only prtiles to rry frtionl eletri hrgeF he theory used to desrie this intertionD the ghD will e presented in detil in setion IFPF 1.1.2 Limitations of the Standard Model hespite eing so fr the most elorted nd suessful theory in prtile physisD the tndrd wodel is still limited in its desription of the universl lws of physisF pirst of llD it does not inlude ny desription of the grvittionl intertionD only fousing on three of the four fundmentl intertions in physisF st n onsequently not e the ultimte theory in physisD if t lest there were to e oneF st is however rrely n issue in itself sD in prtile physisD grvittionl intertion is ompletely negligile ompred to the other ones @pproximtely RH times less intense thn the iw intertion etween proton nd n eletron in the tomAF sn ftD very few physil ontexts require rigorous tretment of oth p nd generl reltivityX the study of the figEfngD lk holes or even neutron strsD whih re wy out of the sope of the present workF enother importnt feture of ontemporry reserh not desried y the w is the existene of drk mtter PSF everl strophysil nd osmologil oservtionsD mde sine the middle of the lst enturies PT!PWD hve shown tht pproximtely WS7 of the mss ontent of the niverse is not visileD thus not mde of ordinry mtter nor interting vi proesses desried y the wF IR IFIF ri exheh wyhiv yp esgvi rsg gonsidering the w itselfD mny elements of the theory re fundmentlly not unE derstoodF edditionlly to the usul disussions on the 4elegne4 of this theory @see for instne QHAD whih depends on PT prmeters to e determined experimentlly in its ontemporry formD it exhiits ompletely irregulr nd unexplined mss hierrhy etween the di'erent fermion genertionsF feyond these rther estheti onsidertionsD whih ould perhps just e how nE ture is mdeD the w nnot explin the mtterEntimtter symmetry oserved in our niverse QIF sndeedD ll intertion it desries onserve oth ryoni numer B nd leptoni numer LD so it nnot e responsile for the ler symmetry oserved nowE dysD if the niverse ws reted without ny imlne in the originl quntities of mtter nd ntimtter s expetedF woreoverD the w su'ered initilly from inomE pleteness regrding the topi of neutrinosF redited originlly s mssless leptonsD it ws disovered in IWWV tht they hve the unique property to osillte while propgting QPF o e expliitD neutrino reted with )vour i nd mss m a D hs nonE zero proility to e deteted with di'erent )vour j nd with di'erent mss m b F he mplitude of these osilltions depends on the elements of mtrix relting the Q )vour eigensttes to the Q mss eigensttes @lled the onteorvoEwkiExkgwE kt @wxA mtrixAD on the di'erene etween the mss eigenstte vluesD on the distne trveled y the neutrino nd its energy QQF reneD suh prtiulr feture requires tht neutrinos hve mssF elthough their osillting ehviour n e dded to the w ad hoc without rising ny inonsistenyD it is not n originl predition of the theory nd omes t the prie of implementing U dditionl free prmeters in itD plus dditionl fetures disussed in the next susetionF pinllyD severl reent experimentl mesurements show ppering tensions with w preditionsF he (rst one onerns the nomlous ontriution to the mgneti moment of the muon (g -2) µ D quntum mehnil orretion to the vlue oming from the hir eqution QRD originlly predited y tulin hwinger for the eletron QSF es mtter of ftD results of mesurements from the wuon g -2 ixperiment in PHPI QTD omined with previous mesurements hieved y the iVPI experiment QUD reveled disrepny of 4.2σ @stndrd devitionsA ompred to w preditionsF enother essentil property of the theoryD lepton )vour universlityD sys tht ll leptons ouple the sme wy to guge osonsD or in other words tht n intertion should our t equl rtes for ll leptoni )voursD side from mss onditionF o test this propertyD it is usul to study deys of hdrons into pir of leptons plus nother hdronD nd to mke the rtio of dey rtes into ertin leptoni )vours lD over the rte of the sme dey into other )vour@sAD whih is then expeted to e equl to IF roweverD severl experimentl mesurements of suh rtios hve shown signi(nt devitions from unity in the pst IH yersF he B → D ( * ) l -νl deys mesured y the ffr ollortionD s well s the B → K ( * ) l + l -mesured y the vrg ollortion hve pointed out devitions of respetively 3.4σ nd 3.1σ from the universlity hypothesis QVD QWF he uthors of RH even limed thtD y performing n nlysis over dt from severl experiments of some hdroni deys implying the b → s l + l -underlying proessD they oserve devition from w preditions y 5σF et lstD reent preise mesurement of the W oson9s mss y the ghp experiment reveled di'erene from w expettion with signi(ne level of 7σ RIF IS grei IF esgvi rsgX pyw riy y iiswix 1.1.3 Beyond the Standard Model he di'erent shortomings of the tndrd wodelD dded to the inresing numer of mesurements yielding tensions with its preditionsD tend to lerly indite tht there re proesses we do not understnd yet whih re out of its rehF reneD this susetion will give glimpse of the reserh led nowdys on eyond the tndrd wodel @fwA physisF he serh for quntum grvity theoryD whih ims t desriing grvittionl inE tertion in the frme of pD would o'er sheme inluding the whole R fundmentl intertions of physisD even though fr from eing trivil prolem to solve QHF st hs een n tive reserh (eld sine the fmous physiist tephen F rwking formulted the lk hole informtion prdox in the middle of the IWUHs dede RPD RQF yne of the numerous intents to mrry quntum mehnis with generl reltivity is the string theory RRD not to e onfused with the string model s will desrie in susetion QFQFRF enother pth widely explored onerns the existene of upersymmetry @AF uh theories postultes the existene of dditionl glol symmetriesD whih would imE ply tht eh existing prtile of the w hs soElled 4superprtner4D hevier nd from di'erent nture @fermions hve osoni superprtnersD nd vieEversA RSF emong the huge diversity of possile theoriesD one n (nd lrge diversity of explntions to the ppering tensions mentioned in the previous susetionD e.g. the lepton )vour uniE verslity violtion or the nomly of the (g -2) µ RTF he experimentl serh for new mssive prtilesD whih would hint for the existene of nd lso disriminte some of those theories in the myrid of existing onesD is n tive (eld for the eve nd gw ollortions t gix RU s well s for the ghp nd hH ollortion t permil RVF he forementioned serh for new prtiles in highEenergy ollisions lso ims t looking for the potentil sign of drk mtter ndidtes RWD in ddition to the numerous experiments entirely dedited to this hunt SHF enother venue tht ould potentilly solve the drk mtter puzzle would e the existene of the sterile neutrinoD n dditionl @if not mnyA )vour of the neutrino whih would not intert with ny guge oson of the wD hene eing not diretly detetle IRF st emerges nturlly when inluding the osilltion mehnism nd msses to neutrinos in the extended wD with this inluE sion eing in some sense lredy fw physis in itselfF sn dditionD its existene hs een hinted experimentlly y nomlies in the mesured )ux of neutrinosD ompred to predited vluesD oserved in di'erent kinds of experimentsF gonsequentlyD welth of new experiments dedited to neutrino physis plns to hve look t potentil signs of sterile neutrinos in their resultsD whether eing mjor or only seondry reserh fous SIF 1.2 Hadronic physics and Quantum ChromoDynamics he lst setion hs set the sene for this thesisD fousing however more on the eletrowek side of the tndrd wodelF sn this setionD s will introdue the other side of itD whih is the min ontext of my workX the quntum hromodynmis @ghAF tust like the other prts of the wD ghD nd even more rodly hdroni physisD still hs mny shdow res nd is even proly the prt of the w whih still hs the most elements to unveilF efter portrying gh nd its min hrteristis in historil mnnerD s will present severl pprohes nd phenomenologil models whih hve een developed to irumvent the di0ulties enountered when intending to use itF IT IFPF rehyxsg rsg exh exw grywyhxewsg 1.2.1 The foundation of QCD he identi(tion of elementry prtiles whih ompose the ordinry mtterD i.e. protonsD pions nd eletronsD s disussed in the introdution of this hpterD ws of ourse not the end of the storyF pirst using osmi rysD nd tking then dvntge of the development of modern prtile elertorsD unh of new prtiles were disovE ered during the IWRH9s nd IWSH9s dedes SPF he lightest onesD with mss inferior to the proton9s oneD were lled mesons @from the qreek mésosD 4middle4A fter rideki ukw9s predition of osoni prtiles rrying the strong intertion etween nuleE ons in the tomi nuleus @ltely identi(ed s pionsA SQF he prtiles hevier thn the protons were lled ryons @from the qreek barýsD 4hevy4A y erhm isD in his work on the desription of the intertion of the newly disovered strnge prtiles SRF fesidesD this sme physiist ws the (rst to propose tht the dey of some of those new prtilesD lled initilly Eprtiles euse of the pttern formed y their deyD ws due to di'erent proess thn the strong intertion SSF st led to the onept of strngeness s property nd new quntum numer of those prtilesD whih were tully konsD Λ nd Σ ± ryons STD SUF sn order to orgnise this soElled zoo of prtilesD suessful model hs een proE posed independently y uvl xe9emn nd wurry qellEwnn in IWTID the fmous 4iightfold y4 SVD SWF hey relised thtD y sorting mesons @of spin J = 0D s osonsA nd ryons @of spin J = 1/2D s fermionsA into two distint groupsD they ould orgnise them s funtion of their respetive hyperhrge Y nd isospin projetion I 3 F hey otined in this wy two representtions of the symmetry group (3) lled otetsD whih re portryed in pigure IFPD sed on the vie lger of group representtion theE oryF his sheme predited the existene of the η meson whih would e disovered soon fter THD nd ould lso e repeted for other groups of identil spin prtilesD whih led to the predition of the Ω -ryon for the J = 3/2 deuplet of ryons for instneF yne in the pth of the (3) groupD it ws relised independently in IWTR y wurry qellEwnn TI nd qeorges weig TP tht more fundmentl symmetry of this group ould e )voursD t the numer of Q in its fundmentl representtionF he uD d nd s )vour qurks thus introdued were supposed to hve frtionl eletri hrge +2/3 nd -1/3F hen ound togetherD they produe the previously shown representtions of the two hdroni fmiliesX qEq pirs form mesonsD nd qqq trios form ryonsF hese elementry prtiles were lled 4qurks4 y qellEwnnD nme whih stuk to them until now @unlike the 4es4 disussed y weigAD even though the uthor didn9t elieve IU grei IF esgvi rsgX pyw riy y iiswix in their existene s rel physil ojets t tht timeF pew months lterD ysr lE le qreenerg TQ nd then wooEoung rn nd oihiro xmu TR proposed the introdution of nother quntum numer for qurksD following n dditionl nd distint (3) symmetry groupF his new hrgeD whih is now known s the 4olour4D ould explin how ryons like ∆ ++ @uuuA nd Ω -@sssA ould exist in the frme of the qurk model without violting uli9s exlusion prinipleF st ws not until IWTW tht qurks were (nlly experimentlly disoveredF tmes fjörken nd immnuel shos interpreted the existene of pointElike prtiles omposE ing hdrons from the results of deep inelsti sttering @hsA t the Stanford Linear Accelerator Center @vegAF fsillyD it ws notied tht the rossEsetion of this inE elsti retion n e expressed with the dependene of only one vrile x @sometimes written x B A like in elsti rossEsetionsD tht is often referred to s the fjörken sling TSF st trnsltes the ft thtD when the energy of the eletron is inresedD the resE olution wvelength of the virtul photon exhnged eomes smller nd the eletron stters smller onstituent of the protonF ihrd F peynmn introdued then the prton model TTD giving hene theoE retil explntion to the oservtions of fjörken nd shosD lling these proton9s onstituents 4prtons4F he frmework of the prton model is n inlusive pprohD formulted to mke lultions for only one exit proessD with ll others wys out eing integrtedF por exmpleD in A + B ⇒ u + X eventD the u qurk for whih one mkes lultion is isolted from the rest of the systemD nd ll other proesses ourring in prllel re integrted in the XF henD eh prton tkes frtion xD of the momentum p nd energy of the hdron it is omposingD de(ned y TUX

V CKM =   V ud V us V ub V cd V cs V cb V td V ts V tb   =   0.
x = Q 2 2p • q = Q 2 2M.ν , @IFPFIA
when using ν = p • q/M = E -E ′ the totl energy exhnged during the intertionD where M is the mss of the protonD q the exhnged photon9s energy nd Q 2 = -q 2 the soElled virtulity of the proess onsideredF yviouslyD the sum of those vriles x is equl to ID nd summing over ll the prtons i with f i (x) = dP i dx their prton distriution funtionD we otinX

i xf i (x).dx = 1 . @IFPFPA
enother importnt ssumption of the prton model is the ft tht prtons re expeted to e lmost freeF es will e disussed in susetion QFQFID this ssumption puts limits on its pplitionF efterwrdsD peynmn identi(ed prtons with the qurks proposed y qellEwnn nd weig TVF roweverD the results of eqution IFPFP pplied to hs on protons nd neutrons indited tht only third of their totl momentum ws rried y qurksD when ssuming their strutures s predited y the qurk modelF gonseE quentlyD there hd to e some eletrilly neutrl prtons in the nuleons thenD whih were thought to e the gluons TVF he lst piee of the puzzle ws rought y hvid qrossD prnk ilzek nd hvid olitzer in IWUQD who proposed to desrie strong intertion with nonEeelin theory of the group (3)D using olor s lol symmetry TWD UHF prom this theory emerged one signi(nt property of ghX the oupling onstnt α s is tully not onstntD ut tends symptotilly to H when inresing the energy sle of the intertionD or when qurks re getting loser to eh other s n equivlent pitureF st n e expressedD in IV IFPF rehyxsg rsg exh exw grywyhxewsg the spei( se of (3) groupX

α s (Q) = 12π (33 -2N f ) ln Q 2 Λ 2 QCD , @IFPFQA
with N f the numer of qurk )voursD nd Λ QCD n infrred utEo' TUF his propertyD lled symptoti freedom s qurks eome free with the symptoti diminution of the strong intertion strengthD hs een veri(ed y mny mesurements s shown in (gure IFQF his sme yerD qellEwnn ginD with rrld pritzsh nd reinrih veutwylerD gthE ered ll the piees to omplete the puzzle of gh UIF hey demonstrte tht the (3) nonEeelin guge theory desries perfetly the strong intertionD in greement with ll previous preditions of the qurk model nd fjörken slingD nd integrtes perfetly olour s hrge of this intertionF hey went even further y ssumingD in greement with oservtionsD tht ll intertions nd physil prtiles oserved hve to e olour singlet @orD s usully sidD 4olour neutrl4AF st trnsltes the ft tht qurks nd gluons n never e oserved s free prtiles eyond the reh of the intertionD of the order of ∼ 1 fmD nd thus re lwys on(ned into hdronsF he experimentl on(rmtion me from the oservtion of two jets events t veg in IWUSD in e + Ee -ollisions t enterEofEmss energy √ s = 7.4 qe UPD UQF tets re ollimted unhes of hdrons whih were predited to emerge from the frgmenttion of qurksD produed in suh ollisions vi the nnihiltion proess e + Ee -→ γ → qEq URD USF ith the sme ide tht gluons eventully mterilise s qEq pir resulting in jetD their existene ws dedued from the oservtion of three jets in e + Ee -ollisions y the vy experiment in IWUWD in the dey of Υ(1S) (cc) → ggg UTF IW grei IF esgvi rsgX pyw riy y iiswix 1.2.2 How to deal with QCD: methods & phenomenological approaches iven though eing well estlished s the theory desriing strong intertionD the nture of the gh mkes it hrd to employF s will hene present in this susetion some of the methods nd pprohes whih re used nowdys to mke lultionsD prediE tions nd simultionsD nd re losely or remotely sed on gh (rst priniplesF he im is indeed not to mke n exhustive listingD ut to introdue the ones whih will e further mentioned nd disussed in this thesisF he running hrter of the gh oupling onstnt restrins for instne the use of perturtive theoryF sn ihD the oupling remins pproximtely onstnt round vlue α = 1/137 @it inreses slightly to higher vlues t high energiesD ut still lose to this vlue for the energies rehed nowdysAD whih llows perturtive lultions whtever the energy sle impliedF yn the ontrryD the vlue of α s in gh only enles to perform perturtive lultion strting from few qeD s n e seen in pigure IFQF roesses t suh energies re often referred to s 4hrd proesses4F husD Λ QCD from eqution IFPFQ n e interpreted s sle elow whih perturtive lultions n not e performed resonlyF xeverthelessD n pproh initited very soon fter the estlishment of gh s (3) guge (eld theoryD lled lttie quntum hromodynmis @lghAD llows to perE form nonEperturtive lultions UUF st onsists of disretising the (eld theory on lttie in iuliden speEtimeD where qurks nd ntiqurks re on sites of the lttie nd edges represent the olour (eldF he min limittions of lgh re of ourse its nonEdynmil ntureD the relted ssumption of therml equiliriumD nd the ft tht the lttie sping hs to e extrpolted to the ontinuum to render physil resultsD whih requires huge omputing resoures IRF iven though this formultion of gh is nonEovrint due to the speEtime disretistionD it opened the gte for preditions of lowEenergy proessesD nd mde on(nement of qurks pper nturlly s (rst suE essful pplitionF st llowed sine to predit the msses of severl hdrons UVD of re qurk msses UWD VH or to study the ehviour of qurkoni @mesons mde up of the sme hevy )voured qEq pirA in medium VIF sn the study of the phse digrm of nuler mtterD lgh is lso widely usedD s will e disussed in hpter PF sn prtiulrD it n e used to lulte suseptiilitiesD whih re diretly relted to the umulnts of onserved hrgesD the oservles t the hert of the study exposed in hpter SF roweverD none of the two previous ghEsed methods enles to mke predition out the dynmil proess of hdronistion ourring in highEenergy ollisionsD whih hs not een proven nlytilly so frF pollowing the onept of on(nement nd the ft tht the potentil of the strong intertion inreses linerly with distneD s proven in UUD phenomenologil pprohes were developed to tret suh importnt questionF yne of them in prtiulrD the string modelD sed on qEq pir retion when strong interE tion potentil energy inreses @lso lled vuum frgmenttionAD will e presented in susetion QFQFRF PH CHAPTER 2 hile hpter I ws devoted to depit the min kground of my workD this seond hpter will fous on the (eld it ddresses in prtiulrX the study of the qurkEgluon plsm @qAF his extremely hot nd dense form of mtter is expeted to hve omE posed our niverse round miroseond fter the figEfng VPD VQF sn order to lern more out its propertiesD we n produe it in hevyEion ollisions @rsgsAD rereting for very short time lpses the ehviour of the erly expnding niverse VRF sn the following setion PFID s will thus present the theoretil knowledge developed round the qD through nother few prgrphs of historyF his will led me to introdue the phse digrm of nuler mtterD whose study omines oth gh nd sttistil physisD leding sine reent yers to even mke link with neutron str studies VSF s will then move on to the experimentl side in setion PFPD where s will introdue some si kinemtis vriles used to study prtile prodution in hevyE ion ollisions @rsgsAD some of whih eing ompred in the (rst prt of hpter S to the results of simultions from iyF his event genertorD designed to ridge the gp etween theory nd experiment in the study of q in rsgsD will e presented in detil lter on in hpter QF hereuponD s will portry some of the pstD urrent nd future experimentl progrms dedited to rsgsD nd desrie shortly the experiments from whih results will e shown in this thesisF s will end up this setion y mentioning severl soft nd hrd key oservles studied to disply signturesD or extrt properties of the qF et lstD in order to ontextulise the mjor study tht s hve ledD exposed in hpter SD setion PFQ will del with the serh for ritil endpoint in the phse digrm of nuler mtterF s will introdue the suseptiilities of onserved hrgesD theoretil tools used to proe the ritilityD nd their experimentl ounterprtsD the moments of netEprtile multipliity distriutionsF xotlyD s will fous on their 2 nd order umulnts nd their rtiosD nd relte the limittions nd mismthes etween these homologuesF s will eventully disuss the results of the two pulitions on whih my study is sedF s will tke this opportunity to strt drwing the lines of my strtegy to mke onnetion etween theoretil developments nd experimentl mesurementsD prepring the ground for the list of my ojetives exposed in setion QFSF 2.1 On a theoretical level: from rst predictions to current models his (rst setion will shed light on the motivtions tht led to investigte the new form of mtter reted in rsgsF s will notly disuss the underlying thermodynmis vi the study of the phse digrm of hdroni mtterD nd highlight the prt of interest for this thesisD i.e. the predition of 1 st order phse trnsition nd ritil endpoint @giA etween hdroni gs nd qF 2.1.1 The theoretical genesis behind the discovery of the QGP huringD nd even efore the tles told out gh in susetion IFPFI hppenedD some physiists were lredy working on phenomenologil models to desrie the ehviour of hdroni mtterF e pioneering work hs notly een hieved y olf rgedornD who introdued his soElled ttistil footstrp wodel @fwA in IWTSD sed on sttistil physis onsidertions VTF he min onjeture ws tht ll hevy hdroni resonnes re omposed of lighter resonnesD themselves omposed of lighter resonnesFFF nd so forth until the lightest possile hdrons @e.g. pionsAD like wtryoshk dollsF reneD pouring energy into suh system will led to rete new light hdronsD forming thus n even hevier resonneD rther thn inresing the kineti energy of the preEexistent PP PFIF yx e riyisgev viivX pyw ps ihsgsyx y gix wyhiv prtilesF es the temperture of medium is preisely relted to the motionD or men kineti energyD of its onstituentsD this ide led nturlly to the onept of mximum possile temperture for hdroni mtterD the rgedorn temperture T H ≈ 158 weF he fw predited thus n exponentilly rising slope for the umultive mss spetrum of hdron resonnesD whih is relted to the deresing exponentil slope of prtile9s momentum spetr VUF sndeedD s they originte from the dey of hevier resonnesD the underlying mehnism is the sme tht led to form those hevy resonnes from lighter ones VVF st is worth notiingD neverthelessD tht preursor work in tht sense hd lredy een pulished in IWSI y ss omernhuk @the sme mn who helped t developing the SEmtrix theory nd inspired the nme of the omeronD oth disussed lter in setion QFQAF re postulted thtD if one ssumes tht pions hve (nite sizeD they ould not exist eyond ertin ritil densityF hen onsidering n idel gs of pions with rdius of 1fmD it would result in similr mximum temperture of the order of T H VWF roweverD suh n hypothesis ws not given reditD s it ws ommonly greed tht pions were pointElike prtilesD t suh erly times efore the ide of hdrons s omposite prtiles emerged WHF king k the history where s left it in the end of susetion IFPFID the qurk model hs een eventully widely epted y physiists one (tted in rigorous theoretil formultion of ghF tust fter the ompletion of the theoryD sungEho vee nd qinE grlo ik suggested in IWUR tht there might exist new stte of strongly interting mtter mde of ontinuum of qurksD ntiqurks nd gluons WIF hey hve een followed y some other uthorsD mong whih tohn gollins nd wlolm erry who went further with the onept of qurk mtter phse t the eginning of the niverse VPF e lot of disussions were then triggered out how to study suh stte of mtterD nd the ide of using reltivisti rsgs ppered nturllyD with the experiments lredy ongoing t the fevl of the Lawrence Berkeley National Laboratory @vfxvA nd t the gix Intersecting Storage Rings @sA WP!WSF sn the mentimeD the theoretil developments on the modeling of rsgs kept going onF iventullyD rgedorn relised tht the T H of his fw ould in ft e reEinterpreted s trnsition temperture etween hdron gs nd q phsesD when onsidering hdrons with (nite volume nd omposed of qurks WTF ome pprohes pretty similr to the fwD prediting n exponentil slope of hdrons sed on trnsition tempertureD nd integrting the notions of qurks nd gluons s elementry onstituents of mtterD hd lso een developed in prllel WUD WVF PQ grei PF ri ryi wei yp ri xsii tmes fjörken proposedD in IWVQD senrio to desrie the expeted speEtime evoE lution of symmetri system in rsgs t ultrEreltivisti energies WWF fsed on some experimentl results of tht timeD he depited tht the system should quikly reh therE ml equiliriumD due to the high energy density nd temperture @⩾ 200 weA rehed t the eginning of the ollisionF efter undergoing phse trnsition to qurkEgluon plsmD the system n e desried s )uidD expnding following the longitudinl ollision xis @usully denoted zA ut lso then rdillyD using hydrodynmi equtionsF he entropy density dereses there s t -1 D implying tht it remins onstnt per rE pidity unit 1 in the entrl regionD whih will result into onstnt prtile prodution per rpidity unit in the (nlEstteF sn this sme entrl regionD the netEryon numer is supposed to e nullD s its initil vlue is rried y the remnnts of the olliding nuleiD loted t high forwrd nd kwrd rpiditiesF efter round dozen of fmG units of time @∼ 10 -22 sAD the system temperture hs deresed due to its expnsionD leding to nother trnsition from q to hdron gs @referred to s hdronistionAF his desriptionD skethed in (gure PFID hs now eome sis for the stndrd piture in the phenomenology of rsgsD s we will see in susetion QFIFPF pollowing this ideD one n see some similrities etween rsgs nd the erly epohs of the figEfngX quikly expnding systemD ooling down from very hot nd dense mtter to dilute smll lustersD in whih initil nisotropies re insried in (nlEstte oservles through hemil freezeEout VRF iven though the size nd time mgnitudes involved re very di'erentD s well s the theoretil frmework used to desrie eh of these two proesses @generl reltivity ginst strong nd eletromgneti intertionsAD it is ommon to ll rsgs s 4vittle fngs4F nder the impulsion of ommunity motivted y the hunt of this qD new proE grms dedited to ever more energeti ion ems were proposed in the erly IWVH9s IHIF xew experiments were thus proposed t the gix IHPD IHQD while it ws even deided to uild new elertor t Brookhaven National Laboratory @fxvAD the rsg IHRF pinllyD the umultion of di'erent results from the experiments shed light on the evidene tht q droplets hd een formed in ollisions involving led ions t gix IHSF he list of experiments involved in the rsg progrm t D whih led to this disoveryD re shown in (gure PFPF he yer of this nnounementD in PHHHD the rsg strted its opertion whih led to the on(rmtionD S yers lterD of the formtion PFIF yx e riyisgev viivX pyw ps ihsgsyx y gix wyhiv of this new stte of mtter in higherEenergy euEeu ollisions IHT!IHWD lthough the forml on(rmtion me in PHIH in IIHF ome detils out the involved experimentsD olliders nd physil signtures leding to this onlusion will e provided in setion PFPF 2.1.2 The phase diagram of nuclear matter xowdysD two dedes hve pssed sine the disovery of the deon(ned stte of nuler mtterF he enter of the relted reserh is of ourse to lern more out its ehviour nd properties of this new form of mtterF sn prtiulrD physiists re inE terested in mpping the phse digrm of nuler mtterD whih displys the reltion etween thermodynmi quntities of the system in therml equiliriumF por the se of mtter desried y ghD it is usul to represent this phse digrm s funtion of the temperture T D nd of the ryoni hemil potentil µ B D whih qunti(es the imlne etween mtter nd ntimtter @qurks nd ntiqurks in this seAF uh phse digrm n e seen in (gure PFQD where the (0, 0) oordintes desrie vuumF tndrd nuler mtter s we know it is loted t T ≈ 0 we nd µ B ≈ 935 weD whih simply orresponds to the rest mss of nuleon tht represents surplus of mtter over ntimtterF sn dditionD we know tht in the low T /µ B regionD qurks re on(ned into hdrons so we tlk out hdron gs phseD while t high T ndGor high µ B D we expet to see them in the q phse @disussed in the previous susetionAF fut where isD or reD the phse trnsition@sAD nd wht re their nture c sn order to nswer this questionD one needs to determine the eqution of stte @ioA of nuler mtterD n eqution whih reltes t lest two thermodynmi vriles of the systemD nd from whih n e derived ll the other quntitiesF roweverD euse of the di0ulties disussed in susetion IFPFPD it is impossile to estlish omplete (T, µ B ) mp from the pure gh theoryF sn the erly IWVH9sD the phse trnsition ws (rst thought to e of 1 st order VUF uh phse trnsition implies disontinuities in the densities of some onserved thermodynmis quntitiesD mening tht the system hnges in disontinuous wy nd experienes heterogeneous oexistene of two phsesD like the liquidGgs trnsition @or oilingA of wter IIIF roweverD the ttistil footstrp wodel for instneD s lredy introduedD ould not give ny lue on its true ntureD s the model diverges t the trnsition temperture T H F woreoverD pplying the desription of n idel quntum permi gs to qurks nd gluons ws not possile either round this tempertureF pollowing nive trin of thoughtsX y using permiEhir sttistil distriE ution to desrie suh system IIID prtons would hve men energy of ⟨ε⟩ ≈ 0.02 qe t T H F his would roughly orrespondD for ollisions used y therml gittionD to typil Q 2 ∼ 0.04 qe involvedD nd thus still very high oupling @looking t (gure IFQAF his mkes lerly impossileD round these temperturesD the use of suh formlism whih is supposed to desrie gs of wekly interting prtilesF xeverthelessD some (rstEprinipleEsed models predited 1 st order phse trnsition t (nite µ B nd low T D some of them even hinting for the existene 2 nd order phse trnsition t higher T D seprted y ritil point IIPD IIQF yn the other sideD mjor step ws tken when (rst lultions from lgh indited rossover @so not rel phse trnsitionA t zero µ B D when onsidering u, d nd s qurks with their physiE l msses IIRF his mens tht the hnge from hdron gs phse to q phse hppensD lthough quite rpidlyD in ontinuous wy nd homogeneouslyF his seems to e on(rmed y experimentl dt from vrg so fr IISF he most upEtoEdte lgh results for the rossover trnsition temperture predits T c = 158 ± 0.6 we IITD in remrkle greement with the predited rgedorn temperture T H F PS grei PF ri ryi wei yp ri xsii utting everything togetherD we know tht the trnsition from hdron gs to q hppens vi rossover t low ryoni density thnks to lghD nd numerous models indite the existene of 1 st order trnsition t T = 0 nd (nite µ B F his tends to indiE tes to the existene of 2 nd order gi somewhere in the phse digrmD s indited in (gure PFQF he serh for the lotion of this gi hs eome mjor ojetive toE dyD nd mny other pprohes hve een used sine to predit its lotionD suh s the hysonEhwinger eqution IIVD the xtv model IIW or the funtionl renormlistion group method IPHF imultions with lgh ould not initilly provide ny predition t µ B > 0 euse of the sign prolemD numeril issue ppering when integrting omE plex exponentil funtionsD enountered when running wonte grlo @wgA simultions to evlute pth integrls for fermioni systems t (nite density IPIF hespite these di0E ultiesD lot of progress in the lst dede hve rought severl methods to extend the preditive power of lgh to (nite densityD using for instne nlyti ontinution from imginry µ IPP or ylor expnsions IPQF hile it is still impossile to predit ny gi with suh methodsD they n t lest indite urvture of the rossover trnsition in the low µ B regionF his serh for the gi is mjor gol of the fi progrmD preE sented in susetion PFPFPD nd spei( motivtion for the work s will present in hpter SF he ojetives of this work will e exposed t the end of hpter Q fter hving introE dued the tool to hieve itD nd the spei( oservles studiedD disussed in setion PFQF he lst region of the phse digrm not disussed so fr is the region of old nd dense nuler mtterD t high µ B nd low T D found in neutron strs IPRF hereD 1 st order phse trnsition hs een preditedD leding to phse of soElled olour superondutivity IPSD IPTF his stteD nlogous to the eletril superondutivity ut for the olour hrgeD is notly expeted to e present in the ore of neutron strsF here hs een revivl of interest in this re ltelyD thnks to the detetion of grvittionl wves from inry neutron str merger IPUF st opened the gte to infer the properties of the nuler mtter omposing themD nd to identify 1st order hdron to qurk phse trnsition IPVD on(rming the existene of qurk mtter in their ore PT PFPF hsxq ri q e ri iiswixev viiv IPWF ineD numerous studies re intending to explore this region of the phse digrm using informtion otined from neutron str mergers nd strophysil oservtionsD ompleting little y little the gret puzzle of the gh phse digrm IQH!IQPF sn reent studyD onnetion hs even een mde etween neutron str mergers nd rsgsD y simulting oth of them using reltivisti hydrodynmis with single io IQQF st shows tht the dynmis of neutron str mergers n e studied vi rsgs performed t √ s N N ≈ 0.5 qeF sn tht respetD it uilds ridge with rsgsD nd dds new motivtion to study them in the lortoryF 2.2 Studying the QGP at the experimental level fefore oming k to the study of the gh phse digrm in setion PFQD s will review the experimentl side of the study of the q in the present setionD eginning with the de(nitions of si kinemti vriles whih will e useful fterwrdF s will then present the min experimentl pprtus @olliders nd detetorsA used to perform nd nlyse rsgsD fousing espeilly on the ones whose mesurements will e ompred to the results of iy simultions in hpter SF s will end up with disussion of the oservles used to proe the existene of the q nd to evlute its propertiesF 2.2.1 Kinematics of high-energy collisions rimordil kinemtis vriles used in hdroni ollisions reD in ny retion of the type

X 1 + X 2 → Y 1 + Y 2 D the wndelstm vrilesX s = (P X 1 + P X 2 ) 2 = (P Y 1 + P Y 2 ) 2 , @PFPFIA t = (P X 1 -P Y 1 ) 2 = (P X 2 -P Y 2 ) 2 , @PFPFPA
with P the REmomentum vetors of the orresponding prtiles here IQRF es n e seen from the formulD √ t represents the energy trnsfer for n elsti ollisionD while √ s is the enterEofEmss energy for n inelsti ollisionF hen deling with rsgsD it is lso usul to tlk out the enterEofEmss energy in nuleon pir frmeD either y inditing √ s N N or y using the qeGe unity s √ s N N = √ sGeF hen hrterising the sptil prmeters of prtiles produed in ollisionD the ommon referene frme tkes its origin t the intertion pointD with the z xis de(ned s the em xisD lso lled longitudinl xisF reneD one usully lls trnsverse plne the (x, y) plneD whih leds to de(ne the trnsverse momentum p T = p x 2 + p y 2 D nd y extension the longitudinl momentum p L = p z F sn order to study the sptil distriution of prtilesD one n use the momentum rpidity y whih mesures the reltivisti veloity of prtile with respet to the frme of oservtionD i.e. the lortoryF roweverD the pseudorpidity η is generlly simpler to hndle in the experimentD euse it is de(ned s funtion of the ngle reltive to the em xisD θF he dvntges of suh vrile re tht it n e esily de(ned geometrillyD without hving to know the mss of the prtile onsideredD nd tht it tends towrds y s the prtile9s speed tends to the speed of lightX

η = -ln tan θ 2 = 1 2 ln | - → p | + p z | - → p | -p z =⇒ β→1 y = 1 2 ln E + p z E -p z . @PFPFQA
foth vriles re null for θ = 90°D in other words when the onsidered prtile goes only in the trnsverse diretionD nd tend to in(nity when the prtiles gets loser to the em xis IRF PU grei PF ri ryi wei yp ri xsii enother extremely importnt notionD when deling with rsgsD is the entrlityF feE use hevyEions hve n importnt trnsverse dimension ompred to protonsD the totl energy involved in inelsti intertions will vryD depending on how muh entrlly they ollide with eh otherD or how muh of their nuleons hve intertedF husD the numE er of prtiles produed @the soElled multipliityA will not e the sme for hedEon ollisionsD referred to s entrl ollisionsD ompred to the peripherl onesD when only smll frtion of eh ion is involvedF roweverD it is not possile experimentlly to infer diretly the vlue of the impt prmeter b of ollisionD whih gives the geometry of the ollisionF yne ssumes then tht the produed prtile multipliityD deteted whether t mid or forwrd rpidityD is proportionl to the numer of prtiipnts of the ollisionD nd y extension to b IQSF reneD to determine the entrlityD experiments exploit the distriution of inelsti rossEsetion s funtion of the hrged prtiles multipliity @or ny relted detetor prmeterAD mesured in spei( kinemti regionF por inE stneD e generlly uses the hrged multipliity within |η| < 0.5 in ll zimuths IQTD while evsgi uses the hrged multipliity distriution in forwrd @2.8 < η < 5.1A nd kwrd @-3.7 < η < -1.7A pseudorpidity regions IQUF yne otinedD this distriution of events is divided into severl entrlity groupsD s funtion of the size of integrted res under the urveD s shown in (gure PFRF he events ontined in the highest HES7 multipliity prt of the distriution re indeed the most entrl eventsD nd the higher the perentge of the lssD the more peripherl re the eventsD y onventionF henD one n use the wonte grlo qluer modelD sed on quntum mehnil pproh of di'rtion IQWD to evlute simple geometril quntities of the ollisionsF fy simulting ollisions with this simple modelD one n reprodue the di'erentil disE triution of the rossEsetion ited erlierD nd evlute for eh entrlity lss the orresponding men vlues of impt prmeter ⟨b⟩D numer of prtiipnts ⟨N part ⟩ or numer of nuleonEnuleon ollisions ⟨N coll ⟩ IQVF roweverD it is only suitle to study suh simple prmeters relted to the erly stges of ollisionD nd not relly relevnt for looking t prtile produtionF PV PFPF hsxq ri q e ri iiswixev viiv 2.2.2 The experimental apparatus sn this susetion re rie)y reviewed the di'erent filities urrently used to elE erte hevy ions t reltivisti energiesD s well s the di'erent experiments studying the ollisions of those hevyEion emsF he emphsis will e put on the rsg nd the Beam Energy Scan @fiA progrm rried out thereD of whih the work presented in hpter S is prtF st will e followed y quik presenttion of the gix omplex nd enggement in the explortion of the gh phse digrmD nd y few informtion provided on the future plnned elertors for hevy ionsF

The BES program at RHIC he Relativistic Heavy Ion Collider @rsgAD the seond most powerful prtile E elertor in the world fter the vrg @disussed fterwrdsAD hs een operting sine PHHHF st is prt of the fxvD loted in the hmlet of pton in vong sslndD xew ork @eAF es the lst prt of n elerting omplexD it is omposed of two storge rings of QFVQ km interseting t T di'erent intertion pointsD using superonduting mgnets to oth fous nd de)et the ems IRHF e totl of four experiments hve tken ple in some of the rsg interting pointsD from whih dt will e shown in the lst hpE ters of the thesisF ell of them were oneived with the sme glol ojetive to mke generl study of the ollisions in whih the retion of q ws expetedD ut eh of them with spei( design proper to their spei( physis golD tking into ount the ost limittionsF he smllest experimentD Broad RAnge Hadron Magnetic Spectrometers @ferwAD ws onduted from PHHH to PHHTF st ws omposed of two spetrometers t forwrd nd mid rpidityD omplementry nd verstileD overing rpidity rnge of 0 < y ≲ 4 with limited zimuthl ngulr eptneD nd p T rnge from ∼H to ∼PS qe for πD K nd p hdronsF he two min prts of the ferw experiment were ompleted with three other suEdetetorsD mong whih two Zero Degree Calorimeters @hgsA ommon to ll experiments t rsg IRIF hese three dditionl detetors were used to hrterise generl properties of reorded ollisionsD suh s luminosityD hrged multipliity nd entrlity IRPF he ryfy experimentD whih took dt from PHHH to PHHSD o'ered full zimuthl overge for pseudorpidity rnge of |η| < 5.4 with its multipliity rryF st hd the prtiulrity to get long with P forwrd spetrometers overing 0 ≤ η ≤ 2 nd only IH°of zimuthl ngle @opposite to eh otherAD dedited to prtile identi(tion t 0.03 < p T ≤ 1 qe with n exellent resolutionF yne of the spetrometer rms ws ompleted y timeEofE)ight detetorD to extend the p T rnge for prtile identi(tion IRQF he seond most importnt experimentD y the size of the ollortion involved nd its dtEtking durtionD is the Pioneering High Energy Nuclear Interaction eXperiment @rixsAF st is mde of two entrl multilyer detetor rmsD with typil struture of multiEpurpose experiment dedited to hdroni physisD involving mny detetor with di'erent pplitions IRRF feuse of the peulir struture of the entrl mgnetD eh of the two entrl rms over only WH°zimuthl ngleD with very limited rpidity eptne of |y| < 0.35F elong the em xisD nd perpendiulr to itD re loted two muon spetrometerD one on eh side of the intertion pointD overing -2.2 < η < -1.1 nd 1.1 < η < 2.4 respetivelyF heommissioned sine PHITD rixs hs lered the wy for its suessorX the srixs experimentF st will inherit from the ylindril superonduting mgneti solenoid of the ffr experimentD enling full 2π zimuthl overge nd n improved pseudorpidity overge of |η| < 1 IRSF PW grei PF ri ryi wei yp ri xsii he Solenoidal Tracker At RHIC @eA is (nlly the most omplete rsg experiE mentD with the lrgest ollortionD nd is the only one still in opertion sine the (rst ollisions hieved in the elertorF fuilt s multiEpurpose experimentD it is lso omE posed of multilyer ensemle of detetorsD nd o'ers n exellent reonstrution nd identi(tion of hrged prtiles in n eptne of |η| < 1 nd for 0.1 < p T qeF he pseudorpidity overge is even lrger for some of the suEdetetorsD nd it n espeilly e extended to the forwrd diretionD to 2.5 < η < 4D y using dedited forwrd time projetion hmer IRTF he rsg hs een used to ollide wide vriety of hevy nuleiD like 64 gu IRU or 238 IRV to ite just fewD ut the ones whih hve een used the most often re 197 eu ions IRWF es the heviest stle nulei elerted thereD they hve een the min protgonists of the fi progrmD strted in PHIHF his progrmD whih onsists of exploring the phse digrm of gh y vrying the ollision energyD involves oth e nd rixs experiments @until the ltter ws stoppedAF he gols re to study the onset of deon(nementD y determining t whih energy the signtures of q formtion pperD to serh for the predited 1 st order phse trnsition nd giD nd for the hirl symmetry restortion ISHF PFPF hsxq ri q e ri iiswixev viiv yne of the min results of the rsgs hieved t rsgD is the oservtion tht the q droplets ehve like n lmostEperfet )uid whih isD in ftD strongly oupledD lthough this sttement might sound ounterEintuitive s qurks nd prtons re deonE (ned in this stte of mtter ISIF his n e understood pretty well when onsidering the simple rguments exposed previously in susetion PFIFPD out the typil vlue of the oupling onstnt for therml intertions of prtons round the trnsition temperE tureF hen looking t (gure PFSD one lerly sees tht for most of the systems reted t rsg energiesD the temperture rehed is too low to ttin smll enough oupling needed to otin gs of qurks nd gluons whih is wekly intertingF enother imporE tnt signl of the fi results so frD is the ft tht severl studied oservles show nonEmonotoni ehviour elow √ s N N ∼ 20 qeF his ould hint tht some importnt hnges in the io of nuler mtter hppen in the reted systemD whih my e used y the existene of the longEsought 1 st order trnsition nd gi ISIF

Heavy-ions at CERN elthough the work presented in this thesis fouses on the fi progrmD it must e mentioned tht gix is lso well involved in the study of rsgsF et low em energiesD the xeTIGSPS Heavy Ion and Neutrino Experiment @rsxiA hs tken over the xeRW experiment ISQD whih ws involved in the disovery of the onset of deon(nement t D disussed y the end of susetion PFIFI ISRF emong the di'erent guidelines of the rsxi physis progrmD n energy sn is hievedD to serh for the predited 1 st order phse trnsition nd giD nd the onset of deon(nement ISSF o do soD the rsxi ollortions mesures the spetr of mny hdroni speiesD in (xedEtrget olE lisions involving protons nd severl ions like 8 feD 40 erD 45 D 129 eD 139 v or 208 D in n enterEofEmss energy rnge of √ s N N ≈ 5 to IUFQ qe ISTF sn this wyD the reserh onduted y this ollortion is omplementry to the fi progrmF he study of q t gix is lso hieved t very high energyD thnks to the most powerful elertor ever uiltD the Large Hadron Collider @vrgAF ith length of PTFUkmD this ring uses the s n injetorD to elerte protons up to reent reord energy of TFV eD thus produing ollisions t √ s = 13.6 e ISUF hespite of dediting most of its em time to proton9s physisD the vrg lso elertes hevy ions suh s 129 e t PFUP eGe ISVD ISWD or 208 up to PFSI eGe ITHD ITID rehing hene energies greter thn the e for E ollisionsF he vrg reretes in this wy the losest onditions possile to the erly stge of the niverseD rehing very high temperture t zero ryoni densityD o'ering the perfet onditions to serh for the origin of mtterEntimtter symmetryF st lso llows to study the soElled old nuler mtter e'ets in symmetri systemsD y performing pEA ollisions ITPF A Large Ion Collider Experiment @evsgiA is the only experiment entirely dedited to the study of hevyEion ollisionsD thnks to full zimuthl overing ensemle of detetors t midE rpidity region @for |η| < 1AD nd forwrd muon spetrometer @t -4 < η < -2.4A minly designed to study qurkoni prodution ITQF iven though eing priniplly foused on the physis of pEp ollisions @e.g. mesurements of w prmetersD jet proE dution or serh for new physisAD A Toroidal LHC ApparatuS @eveA nd Compact Muon Solenoid @gwA experiments of the vrg lso ondut hevyEion progrms ITRD ITSF sn dditionD the lst min experiment loted long the gignti elertorD Large Hadron Collider beauty @vrgAD hs just strted its hevyEion progrm with the reent eginning of the un QD thnks to new devie to perform ollisions on gseous trgets ITTF QI grei PF ri ryi wei yp ri xsii Future facilities o lose this setion on the experimentl e'orts deployed to study the qD quik overview of the future filities dedited to hevyEion study is done hereF sn ner futureD the Facility for Antiproton and Ion Research @pesA is expeted to strt operting in PHPSD t the qs enter in hrmstdt @qiA ITUF helivering ems of protonsD ntiprotons nd ions in the energy rnge of few qeGeD it will llow exploring the very high µ B region of the phse digrm of nuler mtterD s the min reserh purpose of the Compact Baryonic Matter @gfwA experiment ITVF enother fility intending to explore the high ryoni density region in the sme period is the Nuclotron-based Ion Collider fAcility @xsgeA ITWD t tsx in hun @AF st should perform 197 eu em ollisionsD overing rnge of 4 ≤ √ s N N ≤ 11 qe in ollider modeD with Multi-Purpose Detector @whA dedited to hrterise the mtter formed in suh events IUHF e third projetD supposed to strt in the seond hlf of PHPH9s dede t the Japanese Proton Accelerator Research Complex @tEegAD is expeted to proe the sme region of the phse digrmF st is expeted to elerte hevyEions up to 238 in the qeGe energy rnge IUIF sn more distnt futureD suessor to the vrgD nmed so fr the Future Circular Collider @pggAD is plnned to e uilt s IHHkm ollider ring IUPF iven though the question of the nture of prtiles elerted y suh ollider hs not een de(nitely resolved so frD it would llow to hieve E ollisions t √ s N N = 39.4 e or pEp ollisions t √ s = 100 eD if oneived for suh emsF por rsgsD it represents eight times the urrent energies t vrgX suh fility would then ful(l mission opposite to the two previously disussed oneD y exploring the extremely high T region of gh phse digrmF 2.2.3 Methods to study the QGP he lst prt of this setion is devoted to introdue the most ommonly studied oservlesD ssimilted to e signtures of the formtion of qD s well s oservles used to extrt its propertiesF hey re sed on di'erent proesD whih n e lssi(ed into two groupsF Soft probes oft proes generlly refers to prtiles produed thermlly t rther lte stges of the ollisionsD with p T < 2 ∼ 3 qe y onventionD whih re)ets vi their formtion the dynmis nd properties of the qF es we re disussing very hot ulk mtterD the (rst strightforwrd proes to study re the photonsF et low p T D therml photons re indeed expeted to e reted y the prtoni intertions or therml rditions either s rel photonsD or s virtul ones whih mterilise minly vi e + e -pirs IUQD IURF he mesurement of suh diret photonsD whih need to e identi(ed lerly mong the kground mjority of photons reted y hdroni deysD gives ess to the temperE ture of the mtter from whih they originte IUSD IUTF he mesurement of light hdrons spetrum @π ± D K ± nd p/pA llows in turn to get ess to the kineti nd hemil freezeEout prmeters suh s T nd µ B IUUF uh proedure is hieved y (tting the p T spetrD yields nd rtios of the hdrons in question with di'erent modelsF he hemil freezeEout is the moment t whih the yields of ll hdroni speies re (xedX the relted prmeters n thus e extrted from sttistil models sed on the onept of the fw IUVD introdued in susetion PFIFIF he kineti freezeEout prmetersD i.e. when ll intertions etween hdrons eseD n e extrted y using the soElled flst ve wodel IUWF QP PFPF hsxq ri q e ri iiswixev viiv enother signture of the formtion of the q is the strngeness enhnementD the ft tht n overprodution of multiEstrnge @ntiAryons @Ξ -D Ξ + D Ω -D Ω + A is expeted when q is retedF his is due to n enhned prodution of strnge qEq pirs vi q q → ss nd gg → ss proessesD energetilly fvoured in hot thermlised medium omE pred to the retion of strnge hdrons pir in hdron gs IVHF iven more imporE tntlyD one should oserve lower prodution of strnge hdron speies ompred to their vst ut not lestD n importnt oservle to study the olletive ehviour of mtter reted in rsgs is the nisotropi )owF feuse of the pressure grdient etween the extremely hot mtter reted y the ollision nd the surrounding vuumD the medium will expnd nd )ow due to the multiple intertions etween its onstituentsF he sptil symmetries of the originl geometry of the ollision will then e trnsferred into nonEuniform zimuthl distriution of (nlEstte prtiles in the momentum spe IVTD IVUF enisotropi )ow refers to the pourier oe0ient of the zimuthl distriution of momentD denoted v n D with n the order of the oe0ientF reneD v 2 is lled for instne ellipti )ow s it mesures the ellipti symmetriesD v 3 is the tringulr )ow s it mesures the tringulr symmetryD nd so onF he mgnitude of the )ow provides informtion on the level of thermlistion of the medium retedD nd ompring the )ow hrmonis mesurements with simultions of visous hydrodynmis enles to etter onstrin the io of nuler mtterF gonsequentlyD )ow oe0ients hve een extensively studied sine the q hve een (rst oserved @see for exmple IVVD IVWAF st hs notly llowed to determine tht q is the most perfet )uid ever oservedD with the lowest sher visosity over entropy rtio ever mesured of the order of η/s ∼ 0.1 IWHF QQ grei PF ri ryi wei yp ri xsii Hard probes he hrd proesD resulting from hrd stterings hppening t the erly stges of the ollisionsD rry usully lrge energy s onsequeneF he jets re perfet de(nition of hrd proesD eing ollimted ones of hdrons oming from the frgmenttion of highEp T prton @with p T superior to severl qeA produed in hrd stteringF es the prtons inititing the jetsD re reted t the very eginning of the ollisionD they will endure the full evolution of the mediumF sn prtiulrD in the se of q formtionD the prtons will lose energy through elsti ollisions nd mediumEindued gluon rdition whih will result in less importnt ndGor energeti hdron showerX this is the soElled jet quenhing IWIF feuse the retion of hrd prton pir n hppen nywhereD it is usul tht one mong the two prtons hs to trvel lrger distne through the medium thn the otherD nd thus lose more energyD leding to symmetri dijet emisE sionsF his is experimentlly visile vi the unlne of highEp T dihdron zimuthl orreltionD or simply y the suppression of highEp T hdrons when ompred to sled pEp ollisions IWPF he e'ets of jet quenhing hs een oserved oth t rsg IWQD IWR nd vrg IWSD IWTF woreoverD jet quenhing n e exploited to extrt properties of the mediumD suh s the gluon density or the trnsport oe0ient qD whih hrterises the men energy loss per unit length when trvelling through the medium IWPF revy qurks re lso very good hrd proes of the qD s they n only e reted vi the initil hrd stteringsF sn prtiulrD qurkoni @un)voured mesons mde of cc or b b pirsD like J/Ψ or Υ for instneA re studied euseD when trvelling through the deon(ned mediumD they n e dissoited due to olour sreeningF his proessD lled qurkoni suppressionD is thus expeted to indite without ny miguity the presene of qD y ompring their yields from rsgs with sled pEp ollisions IWUF urkoni turn out to then e usle s thermometer of the hot medium in whih it evolvesD s knowing their inding energies enles n estimtion of the temperture rehed y the q when looking t their sequentil suppressionF roweverD some e'ets of reomintion re lso possile t vrg energiesD s hevy qurks pirs initilly proE dued inoherently n ind to eh other while roming through the medium IWVD IWWF urkoni suppression hs therefore een oserved t rsg PHH nd vrg PHID ut less pronouned in the ltter seF elthough hving disussed solely qurkoni physisD the study of hevy )vours in generl is of interest s hevy qurks nD like jetsD provide informtion on the trnsport properties of the q PHPF pinllyD questioning results out the forementioned signtures of the q in smll systems should e ddressedF ine dedeD nlyses of highEmultipliity events for pEp nd pE ollisions t vrg unveil trends suh s strngeness enhnement of ngulr orreltionsD whih re ommonly interpreted s signtures of olletive ehviour of the system PHQ!PHTF gliming tht q is formed in suh systems ould e too premtureD s understnding the proesses leding to these mesurements is still under investigtionD requiring reonsidertion of mny onepts tht were thought to e lerly estlishedF 2.3 Focus on: criticality in the nuclear phase diagram feyond lerning out its very own propertiesD one of the importnt spets of the study of q lies in the knowledge of the onditions in whih it is formedF es lredy explined in susetion PFIFPD n importnt e'ort of tody9s reserh is devoted to serhE ing for the predited 1 st order phse trnsition nd the ssoited giF st is the hert of the Beam Energy Scan progrmD introdued in the susetion PFPFPD nd the motivtion for the min study of this thesisF fut how would the existene of ritil point mnifest QR PFQF pyg yxX gssgevs sx ri xgvie rei hseqew itselfc ht kind of oservles ould e used to serh for its existenec he gi mrks the seprtion etween the 1 st order phse trnsitionD where oth hdroni nd q phses oexistD nd the rossover trnsition where the whole system is under the sme phseF rene the orreltion length of the systemD representing the typil length for whih the elements of the system re orrelted @orD in other wordsD in homogeneous stteAD diverges t tht pointF es the eventEyEevent )ututions of onserved hrgesD mesured vi the umulnts of netEhrge multipliity distriutionD re relted to the orreltion lengthD it hs een suggested tht they ould serve s good proe for the existene of the gi PHU!PHWF he thermodynmi suseptiilitiesD linked to these two vrilesD re lso used s they n e lulted in the frme of lgh PIHF he (rst prt of this setion will then e dedited to the introdution of those quntitiesF huring the pst few yersD mny mesurements of proxies for the forementioned umulnts hve een mde PII!PISD some of those results eing prt of the lues hinting for the interesting physis hppening in rsgs elow PH qeGe @s mentioned in susetion PFPFPAF fut those oservles re lso sujets to shortomingsD in their reltion with their thermodynmi ounterprts s well s in their experimentl evlution Y s will expose these )ws in the seond prt of this setionF st is extremely importnt to sertin nd understnd properly the di'erene etween these oservles nd the theoretil vriles to whih they re reltedF hereforeD s will presentD in the lst prt of the setionD some results from e on the experimentl umulnts used s proxiesD nd theoretil study whih resulted into proposing the use of 4enhned4 proxies to mesure )ututions of the onserved hrges in the experimentF s will explin how this onlusion motivted my workD whih gols will e outlined lter on in setion QFSF 2.3.1 Thermodynamic susceptibilities and net-charge cumulants he theoretil quntities widely used nowdys to study ritility in the phse diE grm with lgh re the soElled thermodynmi suseptiilitiesF sn order to introdue themD let9s strt with si notions of sttistil physisF he grndEnonil @qgA ensemleD used to desrie the systems simulted in lghD gives desription of the sttes of system in thermodynmi equilirium with reserE voirD with whih it n exhnge energy nd prtilesF uh n ensemle is hrterised y its temperture T D its volume V nd one or severl hemil potentil@sA µF he prtition funtion of the system ontins the informtion on how the proilities to (nd the system in given mirostte re distriutedD mirostte eing spei( mirosopi on(gurtion of the systemF st is expressed in the qg @or mrononilA ensemleD for the simpli(ed se of single prtile speieD sX

Z(T, V, µ) = i e -β(E i -µN i ) ,
@PFQFIA with i given mirostteD E i its energyD N i the numer of prtiles whih ompose it nd β = 1/k B T IIIF st de(nes the grndEpotentil Φ G D whih is the genertor funtion of the qg ensemleD vi the reltionX

Φ G = -k B T × ln(Z(T, V, µ)) . @PFQFPA
yne n then otin the pressure vi the derivtion of this grndEpotentil with respet to the volumeD t onstnt µ nd T X

P (T, V, µ) = - ∂Φ G ∂V T,µ = T V ln(Z(T, V, µ)) @PFQFQA
QS grei PF ri ryi wei yp ri xsii @note tht from hereD k B is not expliitly written nymore nd tken s 1D using nturl unitsAF sn the frmework of phenomenologyD one onsiders generlly three hemil potentils for eletri hrge QD ryoni numer B nd strngeness SD wht leds to de(ne the hemil potentil vetor ⃗ µ = (µ B , µ Q , µ S )F he thermodynmi suseptiilities of the onserved hrges (B, Q, S) re de(ned s the derivtives of the dimensionless pressure P/T 4 with respet to the hemil potentils of these hrges PITX

χ BQS ijk = ∂ i+j+k (P/T 4 ) (∂ μB ) i (∂ μQ ) j (∂ μS ) k , @PFQFRA
with the redued hemil potentil μX de(ned s μX = µ X /T F sn this thesis s will only fous on the 2 nd order suseptiilitiesD expliitly givenD when using eqution @PFQFRAD yX

χ X 2 = ∂ 2 (P/T 4 ) ∂ μ2 X , χ XY 11 = ∂ 2 (P/T 4 ) ∂ μX ∂ μY , @PFQFSA
with X, Y = B, Q, SF ytherwise known s digonl nd o'Edigonl orreltors respeE tivelyD the six orresponding quntities n esily e expressed s liner omintions of the qurk numer suseptiilitiesD whih re the quntities diretly essile vi lgh PIHX

χ B 2 = 1 9 (2χ u 2 + χ s 2 + 4χ us 11 + 2χ ud 11 ) , χ BQ 11 = 1 9 (χ u 2 -χ s 2 + χ ud 11 -χ us 11 ) , χ Q 2 = 1 9 (5χ u 2 + χ s 2 -4χ ud 11 -2χ us 11 ) , χ BS 11 = - 1 3 (χ s 2 + 2χ us 11 ) , @PFQFTA χ S 2 = χ s 2 , χ QS 11 = 1 3 (χ s 2 -χ us 11 ) .
yne n link these suseptiilities to the umulnts of netEhrgesD strting k from the de(nition of the grndEpotentil in eqution @PFQFPAF pollowing sttistil mehnisD its di'erentil n e expressed s dΦ G = -P dV -S dT -N dµD with S the entropy nd N onserved numer of hrges or prtiles ssoited to µ IIIF gomes then strightEforwrdly tht the expettion vlue @or menA ⟨N X ⟩ of onserved hrge X is given y the derivtive of Φ G with respet to µ X X

⟨N X ⟩ = ∂ ∂µ X Φ G = T ∂ ∂µ X ln(Z(T, V, ⃗ µ)) = ∂ ∂ μX ln(Z(T, V, ⃗ µ)) , @PFQFUA
relling the de(nition of the redued hemil potentilF sing eqution @PFQFQA to reple the grndEpotentil logrithmD

⟨N X ⟩ = ∂ ∂ μX P (T, V, ⃗ µ) V T = ∂ ∂ μX P (T, V, ⃗ µ) T 4 × V T 3 , @PFQFVA
one eventully (nds the reltion etween the 1 st order umulnt C X 1 of onserved hrge X nd the orresponding 1 st order suseptiility χ X 1 s de(ned in eqution @PFQFRA PIUX

χ X 1 = ⟨N X ⟩ V T 3 = 1 V T 3 C X 1 . @PFQFWA
sn the sme wyD one n derive the vrition of the men onserved hrge X due to the )ututions of ny onserved hrge Y PITX

∂⟨N X ⟩ ∂µ Y = T ∂ 2 ∂µ Y ∂µ X ln(Z(T, V, ⃗ µ)) = 1 T . ∂ 2 ∂ μY ∂ μX P (T, V, ⃗ µ) T 4 × V T 3 . @PFQFIHA
QT PFQF pyg yxX gssgevs sx ri xgvie rei hseqew leding gin to the reltion etween the 2 nd order umulnt C XY 11 nd the orresponding 2 nd order suseptiility χ XY 11 D still sed on eqution @PFQFRA PIUX

χ XY 11 = ⟨N X N Y ⟩ -⟨N X ⟩⟨N Y ⟩ V T 3 = 1 V T 3 C XY 11 @PFQFIIA
his result enles to write expliitly the expression of oth 2 nd order suseptiilities

χ X 2 nd χ XY 11 D nd their reltion to digonl nd o'Edigonl umulnts C X 2 nd C XY 11 D lso usully referred to s vrines σ 2 X nd ovrines σ 11 XY PIUX χ X 2 = ∂ 2 ln(Z(T, V, ⃗ µ)) ∂ μX 2 = ⟨N X 2 ⟩ -⟨N X ⟩ 2 V T 3 ≡ 1 V T 3 σ 2 X , @PFQFIPA χ XY 11 = ∂ 2 ln(Z(T, V, ⃗ µ)) ∂ μX ∂ μY = ⟨N X N Y ⟩ -⟨N X ⟩⟨N Y ⟩ V T 3 ≡ 1 V T 3 σ 11
XY , @PFQFIQA y using equtions @PFQFIIAD nd eqution @PFQFSA with @PFQFQAF fut why re those quntities interesting to serh for the gi c pirst of ll euse they re proportionl to the orreltion length ξ of the systemD whih diverges t the gi Y in prtiulrD χ 2 ∝ σ 2 ∝ ξ 2 ISIF he umulnts nd relted suseptiilities of onserved hrges re then expeted to diverge round the ritil pointD s shown for χ B 2 in the (gure PFUF xote tht higher order umulnts re even more sensitive to ritil )ututionsD s they diverge with ξ like C 3 ∝ ξ 4.5 nd C 4 ∝ ξ 7 ISID lthough they won9t e studied in this mnusriptF eondlyD on more fundmentl levelD one n underE stnd from equtions @PFQFIPA nd @PFQFIQA tht suseptiilities quntify how the prtition funtion Z of the system hnges when vrying the vlues of hemil potentilsF es this funtion rries informtion on the possile mirosopi on(gurtions of the systemD it shll hnge drstilly t the viinity of the giD s the system goes from 1 st order phse trnsition where it is mde of two heterogeneous phsesD to rossover trnsition where it is omposed of only one homogeneous phseF reneD the suseptiilities qunE tifying these vritions should diverge when Z endures suh drmti modi(tionF yn the experimentl sideD it is oviously impossile to mesure diretly the suseptiE ilities in rsgsD s the volume of the system nd the temperture nnot e determined QU grei PF ri ryi wei yp ri xsii on n eventEyEevent sisF xeverthelessD one n hve ess to the umulnts of onE served hrgesD vi the mesurement of the hdroni speies whih rry them in given phse speF iven though ll hdrons nnot e mesuredD in prtiulr the neutrl or shortElived ones requiring to e reonstrutedD wht n indue importnt unertintiesD one uses then the most frequent hdrons formed whih rry the hrges of interestF por instneD one n use pions s proxies for Q PIWD s they represent the mjority of hrged prtiles produed in rsgsY using in ddition protons nd konsD one gets more thn WS7 of the totl numer of hrged prtilesF roweverD Q n lso e mesured diretly without the requirement to identify the prtiles themselvesD into ertin limit thoughD s s will explin in susetion PFQFQ when presenting the results of e used in my studyF ith similr rgumentsD experimentl ollortions suh s e use kons s proxies for strngeness S PPHD nd protons s proxies for ryoni numer B PIRF sn ftD the hoie of suh proxies will e entrl prt of my workD s s will desrie in susetion PFQFQF sn order to ompre experimentl results to theoretil vlues of suseptiilitiesD it is usul then to ompre rtios of netEmultipliity distriutions umulnts for proxiesD to rtios of suseptiilities PIUF he use of suh rtios hs een proposed s they llow to nel the trivil dependene of V nd T D s n e seen from equtions @PFQFIPA nd @PFQFIQAF he 2 nd order umulnts of netEmultipliity distriution of the hdrons tht s will studyD lled @oAvrines of netEhdrons from now onD re expliitly lulted using the formuleX

σ 2 α (= C α 2 ) = ⟨δN α 2 ⟩ -⟨δN α ⟩ 2 , @PFQFIRA σ 11 α,β (= C αβ 11 ) = ⟨δN α δN β ⟩ -⟨δN α ⟩⟨δN β ⟩ . @PFQFISA
rereD α nd β indies refer to ny hdroni speieD nd δN α is the netEnumer of those prtilesD i.e. the numer of suh prtiles n α minus the numer of orresponding nE tiprtiles n α X δN α = n α -n α F xote onsequently tht δN α in these equtions re the equivlent of the netEnumers of onserved hrges N X used previouslyD ut for the prtiles @to use e nottionAF pinllyD ⟨...⟩ denotes the verge over the numer of events used for the lultionF he glol strtegy of experimentl ollortions to sn the phse digrm onsists then of reting systems whih will desrie di'erent trjetories when evolvingD vi the lredy disussed fi progrmD y vrying the ollision energyF he ojetive is to detet ny potentil ritil ehviour of the )ututions of onserved hrges vi the mesure of their proxiesD whih ould e due to pssge through 1 st order phse trnsition or gi PIUF es mentioned severl timesD some results of the fi progrm show interesting nonEmonotoni ehviour for ollisions with √ s N N ≤ 20 qeD in prtiulr in the se of netEprotons umulntsF he rtio κσ 2 = C 4 /C 2 for netEprotons in prtiulrD displyed in (gure PFV @leftAD devites from the oisson seline in entrl euEeu ollisionsD whih is expeted if p nd p multipliity distriutions re independent from eh otherF his ehviour nd the spei( shpe it desries ws predited in PPI for ω 4 = C 4 /C 1 in the se of freezeEout line rossing the ritil region t the viinity of the giD see (gure PFV @rightAF hespite the ft tht κσ 2 nd ω 4 re slightly di'erentD this results remins intriguing nd justi(es the ft to perform the sme mesurements t lower energyD to see if the hrteristi shpe is on(rmedF roweverD mny experimentl e'ets nd ises on the mesured quntities hs to e investigted nd tken into ount efore drwing hsty onlusionsD ompred to the predition sed on pure sttistil )ututions oming from the gi ISID PIUF hese sutleties will e the topi of the next susetionF

Limits and shortcomings of experimental and theoretical observables

here re indeed mny vets to keep in mind when ompring results from ny theoretil predition with mesurements mde in rsgsD nd even simply when deling with )ututions t the experimentl levelF st is thus importnt to ddress them in this thesisD dedited to the study of suh umulnts with the phenomenologil tool tht is n event genertorD in order to understnd my motivtionsF por this resonD s will disuss in this susetion the most importnt onesD ut might omit some of them @whih should e less relevnt for the work s will presentAF s refer hene the reder to the following exhustive reviews ISID PIUD PPP to hve more omplete overview on the topiF he most importnt point to tkle is the ler oneptul gp etween mny theoE retil studies hieved in the qg frmeD like lgh lultionsD nd wht hppens in rsgF sn the former seD the system is onsidered t (xed volume in the in(nite limitD in therml equilirium with het th with whih it n exhnge prtilesD nd only glol onservtion is ensuredF sn the ltter se of rsgs howeverD the system is highly dynmilD temperture nd volume )ututes from event to eventD ut temperture is lso inhomogeneous mong the whole system in eh eventD nd oth glol nd lol onservtion lws pplyF hose disrepnies etween theory nd the experimentl wys to proe ritil )uE tutions points t severl e'ets whih hs to e kept in mind when mesuring netE prtile umulnts in rsgsX everl kinds of )ututions emerge from the eventEyEevent nlysis of netEmulE tipliity distriutions PPPF sn ddition to the therml )ututions of onserved hrgesD whih re sought s they should diverge ner the ritil pointD the iniE til geometry of the ollision will vry from events to events nd use dditionl )ututionsF woreoverD hdronistion of the )uid eing quntum mehnil proessD it results in intrinsi )ututions oth in the kinemti distriution nd in the hemistry of hdrons retedF QW grei PF ri ryi wei yp ri xsii he use of rtios might nel the trivil dependene of umulnts on the volumeD ut it does not prevent from volume )ututionsD whih re soure of unwnted dynmil )ututionsF he umulnts re generlly mesured in entrlity lssesD determined generlly vi the qluer model @introdued in susetion PFPFIAF fut the geometry of the system within given entrlity lss vriesD nd nturlly enhnes the mesured )ututions in wht is lled the entrlity inEwidth e'et @gfiA PPQF hese volume )ututions n e minimised thoughD e.g. y using entrlity lsses s smll s possileD ndGor y using orretion methodD the entrlity inEwidth orretions @gfgAF st onsists of lulting the vlue of umulnt C i for given entrlity lss y verging its vlue C m i through ll ins m of the multipliity distriution in the lss onsideredD weighted y the normlised numer of events ω m in the ssoited multipliity in PPRX

C i = m ω m × C m i = m n m m n m × C m i @PFQFITA
he mplitude of the ritil )ututions whih would e seen if the system reted in rsg rehed the gi hs to e estimted properlyD tking into ount ritil slowingEdown nd (niteEsize e'et of the systemF he orreltion length ξ @nd thus the relted umulntsA re expeted to diverge to in(nity t the viinity of the giD when performing lgh simultions of n in(nite size system during n in(nite timeF roweverD in rsgD the system hs (nite sizeD wht will limit the growth of ξ s it n logilly not e lrger thn the system itself PPSF his (niteE size e'et is even more strengthen y the ft thtD s the system is inhomogeneousD only prt of the whole system would pproh the giF sn dditionD the system would reh the onditions of ritility only for (nite time s it ools down nd nnot thus sty in equilirium in this regionD wht would slow down the growth of ξF king into ount those two e'etsD the mplitude of ξ would then e limited to the order of 2 ∼ 3 fm PPTF yther shortomingsD more relted to the experimentl mesurement of the netEprtile umulntsD will lso hve n impt on the serh for ritil )ututionsF he (rst one is the ft of mesuring the umulnts in the momentum phse speD while it is genE erlly integrted out in theoretil studies PPUF sn order to tke the momentum uts into ount in theoretil lultionsD one n use for instne the rdron esonne qss modelD whih will e presented in susetion PFQFQF he suensemle eptne method @ewAD tking into ount ext hrge onservtionD hs lso een developed reently to improve the omprison method etween umulnts mesured in rsgs nd suseptiilities lulted from theory PPVF fesidesD the detetors used in experiment over only restrited phse spe of the kinemti regionF his n turn out to e prolemti if the essile rpidity window is too nrrowD s the ritil )utution re expeted to hve orreltion rnge of the order of ∆y ∼ 1 PPWF xeverthelessD meE suring )ututions in rpidity window smller thn the whole system hs the dvntge to reprodue pproximtely the qg limitD s the suEsystem n exhnge prtiles with the rest of the system onsidered s het th PQHF purthermoreD one hs to e reful not to mix the set of prtiles used to determine entrlity with the prtiles used to mesure umulntsD wht would led to utoEorreltions e'ets nd derese the signl PIUF e simple solution is to use prtiles from di'erent kinemti region to determine the entrlity of the ollisionD thn the prtiles of interestF pinllyD remins the importnt question of the impt of the hdroni sdes on the )ututions rried y hdroni speies fter hdronistionF everl studies suggested RH PFQF pyg yxX gssgevs sx ri xgvie rei hseqew tht the inelsti ollisions nd nnihiltion of hdrons in this lst stgeD nd the reE sulting hnge in the hdroni hemistry nd kinemtisD impt signi(ntly the signl from potentil )ututions PHVD PQIF his rgument is the min motivtion whih led me to study (rstly the quntittive impt of hdroni sdes on the experimentl umulnts mesured y eD presented in the next susetionF s will then elorte further on the method in setion QFSD one hving presented the event genertor used to perform this workF iven eyond these onsidertions thoughD the hoie of proxies to mesure onserved netEhrges hs to e onsidered refullyF heres umulnts for netEQ n e reproE dued lmost perfetly experimentlly @up to detetor unertintiesAD B nd S require proxies s nonEnegligile prt of the prtiles rrying these hrges re not diretly mesurleF por BD n importnt proess hppening in the hdroni phse is the isospin rndomistionD used y retions p + π 0/-↔ ∆ +/0 ↔ n + π +/0 F uh proesses omE pletely lur the originl isospin distriution of nuleons PQPF yn one hndD uthors of PQP pretend tht suh proess enle to reonstrut umulnts of netEB vi netE p umulntsD whih ontins then the informtion for the whole nuleon ontriutionF xonethelessD it is limed on the other hndD in reent work using mirosopi trnsE port pprohD tht isospin rndomistion prevent from the possiility to reonstrut the proper netEB umulnts from proton distriution PQQF y'Edigonl orreltorD i.e. umulnts involving di'erent onserved hrgesD re lso studiedF sn prtiulrD the ryonEstrngeness orreltions in prtiulr hve een proposed s potentil proe for deon(nement vi the mesurement of the σ pK ovrine PHWF he importne of hoosing good proxy to evlute orretly the )ututions emerging from ritil eE hviour motivted reent studyD on their e'etiveness to reonstrut theoretil qunE tities PQRF resented with more detils in the following susetionD this work inited me to investigte the impt of the hoie of proxiesD ompred to onserved hrges umuE lntsF he ojetives nd glol method will lso e synthetilly presented in setion QFSF

STAR results & enhanced proxies for 2 nd order cumulants

Variances and covariances of net-Q, net-p and net-K multiplicity distributions he (rst pulition whih motivtes the reserh outlined in setion QFSD nd exE posed therefter in hpter SD dels with the systemti mesurement of vrines nd ovrines proxies for B, Q, S y the e experiment PIIF hey presentD for euE eu ollisions t √ s N N = 7.7D IIFSD IRFSD IWFTD PUD QWD TPFR nd PHH qeD the following @oAvrines of netEmultipliity distriutions for identi(ed hrged pD π nd KX

      σ 2 π σ 11 πp σ 11 πK " σ 2 p σ 11 pK " " σ 2 K       . @PFQFIUA
fy onventionD the netEmultipliity distriutions re determined s the di'erene etween the positively hrged hdron distriution nd the negtive one @δN α = n α + -n α -AD to follow the prtileEntiprtile sheme of protonsF hey hve een mesured s funtion of the pseudorpidity window |∆η| < 0.1-0.5 used for the mesurementD nd of the olliE sion entrlity within |∆η| < 0.5D in oth ses for prtiles with 0.4 < p T < 1.6 qeF sn the ltter seD whih will interest me in prtiulrD the vlues of the @oAvrines hve een lulted for HES7D SEIH7 nd eh of the IH7 entrlity lsses for IH7 to VH7D RI grei PF ri ryi wei yp ri xsii using the gfg method introdued in the previous susetionF hey re displyed s funtion of the ⟨N part ⟩ vlue estimted for eh entrlity lss with the qluer model @see susetion PFPFIAF he reson is tht it llows to verify if @oAvrines show liner dependene to N part D s expeted ording to the gentrl vimit heorem @gvAD wht n e seen on (gure PFW for ovrines PIIF o void utoEorreltion e'ets @disE ussed in susetion PFQFPAD the entrlity is determined using hrged prtiles within 0.4 < p T < 1.6 qeD ut in the 0.5 < |η| < 1 regionF fsed on these mesurementsD the following rtios C αβ2 hve een lultedX

C Qp = σ 11 Qp σ 2 p ∼ = χ QB 11 χ B 2 , C QK = σ 11 QK σ 2 K ∼ = χ QS 11 χ S 2 , C pK = σ 11 pK σ 2 K ∼ = χ BS 11 χ S 2
, @PFQFIVA with β lwys referring to the prtile onsidered for the denomintor9s vrineF hey re displyed s funtion of ⟨N part ⟩ tooD nd lso s funtion of the ollisions energy for entrl @HES7A nd peripherl @UHEVH7A eventsD s shown in (gure PFIHF xote tht s refer to the 4Q P ID 4 of the e pulition diretly y 4Q4 hereF e preises 4 P ID 4 for 4identied particles4D euse of n errtum ddressed on the initil pulitionF sn this errtumD new mesurements of @oAvrines implying netEπ re used in ddition to netEp nd netEK to determine the @oAvrines implying netEQ P ID D menE while the rw netEQ distriution ws used diretly in the originl pperF he reson for this hnge is tht in the originl workD netEQ distriution ws determined with unidenE ti(ed prtiles trks in the kinemti region of interestD nd netEp/K distriutions from the susequently identi(ed prtilesF sn suh seD the ft tht p nd K distriutions re not independent from the hrged one requires spei( tretment in the lultions of ovrinesD when orreting from the detetion e0ieny of prtilesF es e ws initilly using ovrine lultion formul whih ssumes independene of the two vooking t the updted dt of PIID the most notle result of this study is the ft tht the rtio C pK D whih shows no entrlity dependene t high energyD hnges its sign elow IWFT qeGeD nd is not entrlity independent nymoreF st is more extly used y the underlying sign hnge of σ 11 pK @see (gure PFWAD phenomenon expeted to e relted to the hnge of the phse @hdroni gs or qA from whih the orreltions riseD s pointed out in PHWF uh results motivted me to study the impt of the hdroni sdes in rsgs on these oservlesD in order to disentngle how muh of the signl e'etively omes from eh of the two phsesD s suh theoretil work is even expliitly requested in the onlusion of the pper in questionF o do soD s will employ the event genertor iyD whih s will introdue in the next hpterF RQ grei PF ri ryi wei yp ri xsii New proxies for the ratios of 2 nd order susceptibilities he seond min spet of my reserh work hs een inspired y theoretil study on the hoie of the proxies used to proe the )ututions of B, Q, S PQRF he uE thors estimted the vlues of 2 nd order suseptiilities of the onserved hrgesD using two di'erent methods to extend lttie quntum hromodynmis preditions t (nite nuler densityX the ylor extension methodD nd the setor methodF henD in order to relte them to netEprtile umulnts mesured in experimentsD they investigted the rekdown of ontriutions to these suseptiilities from eh of the most ommonly reonstruted hdroni speies with the rq modelF he rq model is therml modelD using permiEhir nd foseEiinstein sttistisD nd tking its origins in the ides of the fw presented in susetion PFIFIF he min ssumption of this model is tht gs of interting hdrons in their ground sttes n e desried y gs of nonEinterting hdrons nd resonnes PQUF husD the prtition funtion of suh system n e expressed s the sum of idel gs ontriutions from eh known hdroni resonne RX

ln(Z R ) = η R V d R 2π 2 T 3 ∞ 0 p 2 dp × ln 1 -η R e -1 T (E R -µ R ) , @PFQFIWA with E R = p 2 + m 2 R eing the energy of resonne RD nd the hemil potentil ssoited to eh resonne R eing µ R = µ B .B R + µ Q .Q R + µ S .S R @B R D Q R nd S R
re the vlue of onserved hrges ssoited to eh resonneAF pinllyD d R nd m R re respetively the spin degenery nd the mss of eh resonneD nd η R = (-1) 1+B R will e CI for @ntiAryons nd EI for mesons PQRF his wyD the pressure n then e seen s sum of pressures from the di'erent resonne gsesD nd one n reEwrite the grndEpotentilX

P T 4 = 1 T 4 R P R = 1 V T 3 R ln(Z R (T, ⃗ µ)) . @PFQFPHA
sn the frme of this modelD the suseptiilities n e written X

χ BQS ijk (T, ⃗ μ) = R B i R Q j R S k R × I R l (T, ⃗ μ) @PFQFPIA with l = i + j + k(= 2 in the study in questionA nd the phse spe integrl I R l de(ned sX I R l (T, ⃗ μ) = ∂ l P R /T 4 ∂ μl R @PFQFPPA
gonsidering those de(nitionsD one n esily tke into ount kinemti uts on trnsE verse momentum nd rpidity in the phse spe integrtionD whih is of gret interest when ompring theoretil preditions to experimentl dtF o do soD one hs to modify from @PFQFIWAX

1 2π 2 ∞ 0 p 2 dp → 1 4π 2 y 2 y 1 dy p 2 T p 1 T p T cosh (y) p 2 T + m 2 dp T , @PFQFPQA s well sD for pseudorpidityX 1 2π 2 ∞ 0 p 2 dp → 1 4π 2 η 2 η 1 dη p 2 T p 1 T p 2 T cosh (η) dp T . @PFQFPRA RR
PFQF pyg yxX gssgevs sx ri xgvie rei hseqew he min result of the study in PQR is to propose rtios of proxies @denoted Cαβ A whih re enhned versions of the ones used y experimentl ollortions @see equE tion @PFQFIVAAF o do soD the uthors used the eqution @PFQFPIAD from whih they ould estimte the rekdown ontriution of eh hdroni speie to the totl digonl nd o' digonl 2 nd order suseptiilities of BD Q nd SF por instneD the rekdown ontriE ution of di'erent hdroni speies to χ QS 11 nd χ S 2 re displyed in (gure PFIID ompred with the orresponding totl suseptiilitiesF hey tried then to onstrut severl good proxy rtiosD following the rgument tht to do soD it is importnt to use in oth numertor nd denomintor @oAvrine proxies tht re eqully good to reonstrut their respetive relted suseptiilitiesF por the strngeness relted rtiosD whose omprison to ext suseptiility rtios is shown in (gure PFIPD the proposed est enhned proxy rtios re the followingX

CQS = 1 2 . σ 2 K σ 2 K + σ 2 Λ ∼ = χ QS 11 χ S 2 , @PFQFPSA CBS = σ 2 Λ σ 2 K + σ 2 Λ , C′ BS = σ 2 Λ + 2σ 2 Ξ + 3σ 2 Ω σ 2 Λ + 4σ 2 Ξ + 9σ 2 Ω + σ 2 K ∼ = -χ BS 11 χ S 2 , @PFQFPTA
still with the sme onvention tht the seond index orresponds to the hrge of the rtio denomintor9s vrineF he hoie of these enhned proxy rtios is sed on the ft tht they hve to e lose to the ext suseptiility rtiosD ut should exhiit s well similr ehviour over the whole temperture rngeF st is worth notiing tht these enhned proxies re only mde up of vrinesD nd not ny ovrineD sed on the simple ft tht the hdroni speies employed rry severl of the onserved hrgesF xote lso tht the negtive sign in the reltion of χ BS 11 to its proxies is simply due to the ft tht strnge ryons rry B = 1 nd S < 0D s s qurks ssoited to negtive strngeness y onventionF sn prtiulrD two proxy rtios re proposed to evlute the ryonEstrngeness orreltionX one using only K nd ΛD nmed here CBS D nd nother using in ddition multiEstrnge ryons Ξ nd Ω @whih re however more di0ult to mesure experimentlly with redued unertintyAD C′ BS F edded to the ide of studying the impt of hdroni sdes on the proxies emE ployed to proe the )ututions of onserved hrgesD the results of this theoretil work motivted me to go even furtherF ht is to syD to test the proposed enhned proxy rtios ginst the experimentl oneD y ompring in ddition oth of them to the )uE tutions of ext onserved hrgesD in order to see how muh the reonstrution of these RS grei PF ri ryi wei yp ri xsii )ututions would improveF henD following up on from my (rst ideD s n lso study the impt of hdroni sdes on the enhned proxies nd on the umulnts of ext onserved hrges themselvesF uh reserh work requires relisti dynmil simulE tions of rsgs to relte properly the two experimentl nd theoretil studies presented previouslyD wht is gin possile thnks to n event genertor like iyD presented in the following hpterF CHAPTER 3 efter hving dedited the hpters I nd P to introdue the physil ontext of my hFhF thesisD nmely hdroni physis nd more prtiulrly the study of the qD s will introdue in this third hpter the Energy conserving quantum mechanical approach based on Partons, parton ladders, strings, O-shell remnants and Saturation of parton ladders @iyA event genertorF st hs een the hert of ll the work s hve hieved during this thesisD oth euse my min ojetive ws to ontriute to its development in view of puli releseD nd euse s used it to ondut the studies s hve ledF trting with short presenttion of wht is n event genertor @iqA in setion QFI nd little glimpse of the role of suh toolD s will then relte quikly in setion QFP the hronology of the di'erent developments nd projets tht hve led to mke wht iy is nowF setion QFQ will ontin the desription of the theoretil foundtions on whih iy reliesD espeilly the ones tht re exlusive to this iqD leding to the setion QFR in whih s will explin how events re generted with iyF pinllyD s will present the min gols of my thesis in setion QFSD reltive to the new tehnil developments s implemented in iyD nd to the study s hve rried out on the umulnts of netE hrges nd netEprtiles used for the serh of ritility in the phse digrm of nuler mtterF 3.1 Generalities on event generators he mjor developments hieved on modern physis nd on new tehnologies in the erly twentieth entury hs inevitly led to intertwine the history of physis nd informtis sine thenF xumerous progresses in oth (elds were due to disoveries or motivted y requirements from the other disiplineF e fmous exmple is the World Wide WebD whih ws developed y sientists of the gix in order to filitte the exhnge of informtion etween ollortors vi omputer networksD eventully used in the snternetF he other wy roundD the limits of omputing tehnology hve often een pushed to stisfy physiists requirementsX some elements of the (rst omputers were reted for the need of nuler physisF xowdysD highEenergy physis @riA requires enormous omputing resouresF es lwysD oth experimentl nd theoretil ommunities re onernedX the dt )ux olE leted from detetors re onstntly growing upgrde fter upgrdeD with the ontinuous inrese of olliders luminosity @e.g. in the ontext of the High-Luminosity Large Hadron Collider @rvEvrgAAD nd on the other hnd one neessittes ever greter preision in lultions to evlute model prmeters extrted from these dtF imultion tools re lso of primry interestD euse of their entrl role in the omprehension of experiE mentl oservtionsD whether to understnd nd quntify detetor e'etsD or to onfront results with theoretil preditionsF his lst point is the purpose of iqsD whih will e disussed in this setionF

Event generators & high-energy physics

ivent genertors re omputer ode whih ims to reprodue prtile prodution y simulting the dynmis of ollision step y stepF sn the ontext of riD n event refers to everything tht hppens etween the intertion of the olliding prtiles nd the list of (nlEstte prtilesD in similr sense of n event reonstruted in n experimentF RV QFIF qixievssi yx iix qixiey roweverD suh events re very omplited to ompute due to the omplexity nd diE versity of underlying proesses t di'erent stges of the ollisionF hey imply t the sme time perturtive lultions whih re sometimes diretly omputle @up to ertin preision order thoughAD ut lso modelling of nonEperturtive proesses whih nnot e derived from (rst priniplesD nd whih require prmetristionD like the prolem of on(nement whih is responsile for hdronistionF woreoverD hndling suh prolem requires to del with very lrge nd vrying numer of prtilesD thus with phseEspe of very lrge numer of dimensionsD nd the quntum nture of those prtiles neesE sitte proilisti pproh of their intertionsF portuntelyD suh forementioned prolems o'er perfet plyground to pply wonte grlo @wgA tehniquesD in prtiulr thnks to the possiility to ftorise mny di'erent proesses ording to their energy sle regimeF wg methods rely on the genertion of rndom numers tht re used to reprodue stohstilly known distriution of given proessesD y using funtion inversion ndGor hit-or-miss methodF hey n lso e used to evlute numerilly highly multiEdimensionl phse spe integrls nd solve integroE di'erentil equtionsD tht re ommonly met in ri s previously explined PQVF es onsequeneD iqs re fully suited tools to do phenomenologyF hey enle physiists to ompute models nd theories in order to onfront them with experimenE tl dt nd therefore vlidte themD or extrt model prmetersD ut lso to help t disovering nd interpreting newly oserved phenomenF hey re employed to design future experiments nd filities like the ones disussed in susetion PFPFPD or to estimte systemti unertinties in the reonstrution of events with detetorsD when omined with simultion tool kits of prtileEmtter intertion like qiexR PQWF he(nitelyD iqs re the ornerstone of modern prtile physisD the hert of the interply etween theoretil nd experimentl ommunitiesF roweverD they lso ome with some )wsD euse of their phenomenologil ntureX they generlly neessitte prmetristionD nd one hs to e reful out their limited ppliilityF here exists myrid of iqsD due to the numerous (elds of interest in riX neutrino physisD osmiEry showersD testing the w orD s it is indeed the min fous of this theE sisD hevyEion physisF xeverthelessD mny physis elements n e ommon ross these topis despite this diversityD often leding to 4modulr4 oneption of the dedited simultion toolsD whih prts n e used in di'erent (eldsF purthermoreD iqs n e more or less elortedD in other word o'ering more or less omplete desription of the events studiedD depending on the purpose for whih they re developedF reneD there is spei( lss of iqsD lled generlEpurpose event genertorsD whih im is to reprodue rther exhustive rnge of proesses nd oservles of interestF iven though primrily dedited to hevyEion physisD iy is onsidered to e generlEpurpose iqD s its gol is to o'er omplete nd uni(ed desription of di'erent systems suh s e + Ee -nnihiltionD eEp sttering nd from pEp to AEA ollisionsD thnks to the rih legy inherited from its predeessor whih s will introdue in setion QFPF st lso tkes dvntge of 4modulr4 designD wht is prtly due to its trgeted sope of pplition thoughD s s will disuss in the next susetionF 3.1.2 Event generators for heavy-ion collisions hen simulting prtile ollisions for smll systems in the ontext of olliders physisD i.e. pEp ollisions in the vrgD iqs usully generte t (rst the hrdest suproE ess of the eventD efore ompleting the evolution of the event with other suproesses RW grei QF ri iy iix qixiey y deresing order of energy sle involvedF his is minly due to the ft tht in this (eldD the fous is generlly put on hrd intertionsD whether to study w prmeters vi exlusive prodution of guge osons for instneD or to investigte the 4rest4D i.e. the underlying event @seondry stterings tht re independent of the primry hrd proessesA PQVF yn the ontrryD iqs used for the simultion of rsgs generte events in more trditionl timeEordered wyD following the fjörken senrio desried in suE setion PFIFID euse the im is generlly to study the properties nd signtures of qF hey strt with the modeling of initilEstte intertion implying multiple stteringsD whih n e s simple s the qluer model IQW introdued in susetion PFPFID tht llows totl rossEsetion lultions in the optil limit IQVF por instneD rsg event genertors rstsxq PRH nd rse VGengntyr PRI use enhned versions of wgE qluer model to generte their initilEstte intertionF ome other pprohes inlude golorEqlss gondenste e'etive (eld theory @ipAD whih desries the dynmis of olliding nulei s sturted gluon (elds PRPF he seond ommon step in iqs of rsgs is to simulte the evolution of the systemD generlly y using trnsport theories whih n e either mrosopi or mirosopiF sn the mrosopi seD the prtoni degrees of freedom re supplnted y n energyEmomentum tensor in order to mke the system evolve using reltivisti hydrodynmisD ssuming lol therml equilirium PRQF sn the mirosopi seD kineti theories re used in order to keep prtons or qusiEprtiles s degrees of freedomD suh s in rh PRR or ew PRSF sn order to ome k to hdroni degrees of freedomD hdronistion hs to e hieved thenD whtever the nture of the medium evolution hosenF iventullyD models suh s rwh PRTD PRU or wer PRV n e used s fterurners to model intertion etween remining hdronsD until the system rehes kineti freezeEoutF st is this stge of the ollision when hdroni intertions ourD or more preisely its impt on )utution oservlesD tht will e the hert of my study in hpter SF Figure 3.1: Schematised general structure of an event simulated with HIC event generators.

sn the previous desriptionD s intentionlly didn9t disuss the inlusion of jetEquenhing e'ets @how jets re modi(ed y the presene of hot nd dense mediumD nd vieE versAD neither how to tret the trnsport of hevyE)vours through the qD in order to desrie t (rst simple pitureF his is lso euse suh tretments re not systemE tilly si ingredients of rsg event genertorsD whih re generlly primrily foused on the study of 4soft4 physisF fut the implementtion of suh e'ets existsD nd mny works re still ongoing on these very tive reserh topisF eout jetEquenhingD one n see for instne Heavy Ion Jet INteraction Generator @rstsxqA PRHD Jet Evolution With Energy Loss @tiivA PRWD Dynamical Radiative and Elastic ENergy loss Approach @hiixeA PSH or even Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope @tigeiA PSID frmework inluding pkges of di'erent modelsD giving to the user the hoie of desired modulr oneption to generte the eventsF iven though no tul iq dedited to rsgs simultion inlude proper desription of trnsport hevyE)vours through the qD severl pprohes under development or lredy well dvned re ville PSP!PSSD nd ould @or re lredy on their wy toA e oupled with iqsF SH QFPF e vsvi rsy yp iy exh iveih ytig iy follows in some wy this lssil piture of iqs for rsgsD s will e depited with more detils in setion QFRF xeverthelessD it is sed on tretment of initil onditions whih is di'erent from the ones previously desriedD wht mkes it unique pprohF fesidesD iy lso served s sis for the pplition of some jetC)uid nd hevyEqurksC)uid intertion modelsD whih re shortly presented in setion QFPF 3.2 A little history of EPOS and related projects his setion ims t giving rief overview of the development history of iy in the (rst pleD efore desriing shortly the di'erent extension nd projets derived from itF 3.2.1 From VENUS to EPOS 4 he very (rst nestor of iy ws the Very Energetic NUclear Scattering @ixA model PSTF st is n event genertor sed on multiple intertions modelD the qriovE egge theory @qA PSU @see explntions in susetion QFQFPAD oupled to the string frgmenttion model Artru-Mennessier O-shell Resonance @ewyA inspired y PSVD desried in susetion QFQFRF st ws developed in the lte VH9sGerly WH9s to desrie soft proesses ourring in rsgs hieved t the nd Alternating Gradient Synchrotron @eqA elertorsD nd ws one of the (rst event genertors for rsgsF sn order to inlude hrd proesses to the shemeD ix ws lter merged with Quark-Gluon String Jet @qtetA PSWD prton modelEsed iqD giving irth to the soElled neXus event genertor PTHF st relied on the rtonEfsed qriovEegge heE ory @fqAD mrrige of the initilEstte models from oth initil iqs @more detils given in susetion QFQFQAF roweverD nonEliner e'ets needed to e tken into ountD either y reEsumming digrms up to llEordersD t the ost of violting energy onserE vtionD or y implementing n e'etive sturtion utEo' in to order to keep onserving energyF es onsequeneD the neXus projet splitted into two new event genertorsX qtetEss followed the (rst pth with the min ojetive to e pplied mostly to ultrE high energy osmiErys @rigsA physis PTID while iy ws oneived to study more prtiulrly olliders physisD thus following the seond pth ensuring energy onE servtion PTPF purther mjor developments led to new version lled iy P PTQF e oreEoron proedure hs een introduedD onsisting of seprting t n erly time of the ollision the ore prt @re of high string densityA from the oron prt @re of low string densityA PTRD strings eing phenomenologil ojets representing prtoni hinsF he ore prt hs then een set to evolve following perfet QCIh reltivisti hydrodynmisD using rossEover trnsition io whih mthes lttie lultions nd onserves BD Q nd S PTSF et lstD the )uid is hdronised using gooperEprye proedure PTT when ooling down to spei( temperture T Had = 166 weD nd the formed hdrons n reEstter through hdroni sdes modelled with rwh PRUD lso freshly implemented s n fterurnerF he dvent of iy Q rought n upgrde of the oreEoron seprtion proedureD no longer stti ut llowing highEp T string segments to espe @see setion QFRAD nd new visous hydrodynmil evolution of the ore PTUF yn the level of primry interE tionsD huge work hd lso een done to tret properly the prodution of hevyE)voursD SI grei QF ri iy iix qixiey nd the sturtion sle hd een hnged from onstnt to vlue depending on the numer of prtiipnts of the ollision @N part A nd on the energy shred y eh prtoni ldder @or omeronD in the fq formlismAF ine thenD severl improvements hs een hievedD leding too new version now pulily villeD lled iy R PTVF he work hs een ontinued on the tretment of sturtionD nd the relted questions of ftoriztion nd inry sling PTWF e new io inluding ritil point nd 1 st order phse trnsition from PIV hs een impleE mented for the hydrodynmil evolution of the oreD in order to improve the desription of lowEenergy ollision from the rsg PUHF sn ddition to the qg gooperEprye pE proh for hdronistionD new mirononil pproh hve een implementedD giving etter desription of results from smll systems @nmely pEp nd pEA ollisionsAD where energy nd )vour onservtion ply n importnt role PUIF he hdronistion ondiE tion of the oreD whih ws so fr triggered when temperture ooled down to vlue T Had = 166 weD hs een repled y riterion on energy densityD eing now triggered when ϵ < 0.57 qeGfm 3 PUHF e sustntil nd no less importnt work hs lso een undertken on the usility of the odeD its mintinility nd the interfe with other tools suh s ivetD for wht s dedited onsequent mount of time nd e'orts during my hhF s will introdue my ontriutions to this work in the lst prt of this hpterD nd dedite hpter R to give n inEdepth desription of itF 3.2.2 Side projects with EPOS sn prllel of the developments rried out on iy itselfD severl lterntive projets sed on iy re orn over the yersD mong whih iyEvrg PUP is proly the most fmous oneD s eing pulily villeF st is n extended version of iy IFWW PTPD tuned to reprodue dt of severl experiments from the (rst vrg runF st ene(ts from prmetrised )ow of the ore @using the sme oreEoron proedure thn in iy PAD hieved y enforing rdil nd longitudinl expnsion of ore lusters depending on their mssD nd imposing n zimuthl nisotropyF his llows in prtiulr to perform simultions muh more fster thn when using omplete hydrodynmis lultionsF hespite resultnt preditive power tht is reduedD this dvned prmetristion hs een mde with the prtiulr ojetive of implementing iyEvrg into the extensive irEshower @ieA simultion frmework COsmic Ray SImulations for KAscade @gyE sueA PUQF st estlishes this wy ridge etween ollider physis nd rigs physisD nd it hs the tehnil sset of eing wy fster to generte events thn iy P nd more reent versionsD whih use omplete eventEyEevent hydrodynmil simuE ltion of the ulk mtterF he iy Heavy Quarks @iyErA projet PUR hs emerged from the mrrige of iy nd the wg@ s r energy loss model PUSD with the im of studying the orE reltions etween light hdrons nd hevy )voursF he ltter model is sed on wg tretment of the foltzmnn eqution for hevy qurks @rsAD with n energy loss modelled y ollisionl prt @inluding inelsti nd elsti stteringsA nd rditive prt @inluding oherent nd inoherent gluon rditionAF imeEdependent temperture nd veloity (elds of the hydrodynmil evolution of the ore simulted y iy re thus used to smple therml sttering prtners for the rsD whih hdronise then vi frgmenttion or olesene proessF sn the (rst version of this pproh PUTD iy P ws solely used for its hydrodynmis modeling s kgroundF he rs were inserted 4y hnd4 t the position of initil N N stteringsD with their initil p T Edistriution oE SP QFQF riyisgev pewi yp iy tined from pyxvv lultions PUUF he ltest version of iyEr took dvntge of the prodution of rs properly implemented in the fq formlism of iy Q @s desried in the previous susetionAD s well s the visous hydrodynmis nd the (nl reEstterings of hevyE)voured hdrons through rwh PUVF sn prllelD similr pproh hs een developedD lso using initil onditions from pyxvv nd iy P hydrodynmisD ut employing then igner densities sed on the emler formlism to study J/Ψ prodution in AEA ollisions t vrg energy PSRD PUWF iyQEtet is frmework uilt using iy Q s selineD oupled with wg lgorithm of the hokshitzerEqriovEviptovEeltrelliErisi @hqveA eqution PVH to simulte the evolution of the prton sde leding to jet within the q in rsgsF he prton shower will e modi(ed y the medium in whih it evolves vi n e'etive inrese of o'Eshell prtons9 virtulity dependent of the lol tempertureD nd lso vi tempertureE nd momentumEdependent ollisionl termsF he other wy roundD the energy lost y the shower will e dded vi soure term to the energyEmomentum tenE sor of the lol )uid ells to trnslte the impt of the jet on the medium PVIF his frmework hs een used to study the intertions etween jets nd the hydrodynmiE lly expnding medium PVID nd to study the overlpping of jets in this ontext PVPF he lst mjor projet involving iyD lled iyiCrhe PVQD is n hyrid event genertor mixing initil onditions from iy PVR nd the nonEequilirium trnsE port evolution of the mtter from rh PRRF st hs een developed in order to disE entngle initil nd evolution e'ets on severl (nlEstte 4ulk4 oservles @rpidity density of hdronsD )owD etFAD vi systemti omprison of the results otined from oth iyD iyiCrhe nd rhF o sum up this setionD hronologil timeline of the di'erent versions of iyD nestors nd side projets is displyed in pigure QFPD sed on the pulition dte of the orresponding referene ppersF 3.3 Theoretical frame of EPOS fefore to desrie how events re generted in iyD this setion will e used to introdue rie)y the min theoretil onepts ehind some key ingredients of iyF howing some limits nd inonsistenies of the prton model nd the q will led to explin how the fq mrry oth pprohes y uring their respetive prolemsF st will e followed y short presenttion of the string model used to simulte the evolution nd mnge the hdronistion of prton hins in phenomenologil wyF SQ grei QF ri iy iix qixiey 3.3.1 Parton Model he pproh of the prtons modelD introdued in ghpter ID onsists of ftorising the inlusive rossEsetion of two hrd prtons prodution from hdroni ollisionD s produt of the sum of ll prton distriution funtions @hpsA times the elementry prtoni rossEsetion dσ/dp T 2 of the proess TUX

σ h 1 h 2 →q 3 q 4 incl. = partons i,j dp T 2 f i p 1 (x 1 , p 2 T )f j p 2 (x 2 , p 2 T ) dσ q i q j →q 3 q 4 dp T 2 θ(p T 2 -Q 0 2 )dx 1 dx 2 .
@QFQFIA rereD f i,j p 1/2 (x 1/2 , p T 2 ) re the foreEmentioned hpsD whih represent the proility denE sity tht the prton i/j of the hdron h 1/2 hs fjörken vrile equl to x 1/2 for proess hppening t given p T 2 F hile the hps neessitte to e extrted from dtD the elementry prtoni rossEsetion n e lulted diretly with peynmn digrmsF he ftoristion is mde possile thnks to the ermovskyEqriovEunheli @equA nelltions PVSD nd n e interpreted s n inrese in the resolution of the invesE tigted prolem from the hdroni sle to the prtoni sleF ememerD from its introdution in hpter ID susetion IFPFID tht one of the min ssumption of this model is tht the prtons re onsidered s lmost freeF gonsequentlyD the min limittion of the prton model omes oviously from the ft tht it n only e pplied to inlusive rossEsetion lultionsD involving hrd proessD i.e. implying lrge Q trnsferredF his is lerly visile in the eqution QFQFID with the reviside funtion θ(...) tht introdues expliitly virtulity utEo' Q 0 D ut lso hidden in the lultions of elementry prtoni rossEsetions vi peynmn digrmsD whih re only hievle in perturtive regimeF sn dditionD its inlusive pproh nture llows to lulte rossEsetions for one proess in the ollisionD ut there re no inditions on how to proeed for the other proessesD like how to shre energy etween the di'erent proesses in se of multiple prton intertions @wsAF en illustrtion of this prolem is the ft tht eyond √ s ≈ 2 eD the inlusive jet rossEsetion exeeds the totl rossEsetion of the hdroni intertion PVTF iven if one n void this prolem in hdronEhdron ollisions with the soElled eikonlistionD the prolem remins when treting nuleusEnuleus ollisionD s one nnot simply ssume the totl rossEsetion there to e sum of individul nuleonEnuleon intertion rossEsetions PVRF 3.3.2 Gribov-Regge Theory he min formlism on whih the qriovEegge theory @qA is sed is the SE mtrix theoryD derived from quntum mehnis y erner reinsenerg PVUF st relies on the ssumption tht the elsti mplitude is in ft the projetion of the trnsition mtrix T f i D the intertion term of the sttering mtrixF his mtrixD ŜD reltes initil nd (nl sttes of sttering proessF st is expressed s PVUX

Ŝ = 1 + T =⇒ ⟨f | Ŝ|i⟩ = S f i = δ f i + i(2π) 4 δ(p f -p i )T f i @QFQFPA
nd is linked to the totl rossEsetion of the onsidered proess y the optil theoremD through the reltion PVRX

σ tot (s) = 1 2s × 2 × sm[T f i (s, t = 0)] @QFQFQA
gontrry to the prton modelD the qriovEegge theory hs een estlished in IWTV PSU to desrie soft proesses in the frme of wsD in mrge of the development of the qurk model presented in susetion IFPFIF hereD intertions hppen vi the SR QFQF riyisgev pewi yp iy exhnge of 4omerons4D hypothetil mthemtil ojets tht represent elementry intertionsF gonsequentlyD these ojets n simply e prmetrisedD nd the elsti mplitude T P (s, t) for unique omeron exhnge is given y PVRX T P (s, t) = i s α 0 +α ′ t @QFQFRA with α 0 nd α ′ experimentl prmetersD s nd t the wndelstm vrilesF sn hdronEhdron ollisionsD mny omerons re exhnged in prllelD nd the totl rossEsetion n e rewritten s PVRX

σ h 1 h 2 tot (s) = G f i (s, b) d 2 b @QFQFSA
where b is the impt prmeter etween the two olliding prtiles onsideredF rere G(s, b) is the soElled pro(le funtion representing the omeronsD nd n e interpreted s the proility density to hve n intertion t given bF st is de(ned s the imginry prt of the pourier trnsform of T (s, t)D divided y the initil prton )ux 2sX

G f i (s, b) = 1 2s × 2 × sm 1 4π 2 e -i ⃗ q T . ⃗ b T f i (s, t) d 2 q T @QFQFTA with onsidering t = -q T 2 PVRF
he min prolem of this pprohD pointed out in PVVD is tht eh omeron tkes the entire energy of the hdron in rossEsetion lultionsD whih will inelutly led to violte the energy onservtionD s severl omerons re exhnged in one retionF sn dditionD the theory is even more inonsistent tht the energy is however still onserved for the prtile prodution lultions in ll the pprohes sed on the q PVRF 3.3.3 Parton-Based Gribov-Regge Theory he rtonEfsed qriovEegge heory @fqA hve een introdued to merge the two previous pprohes y treting onsistently oth prtile prodution nd rossE setion lultionsD while onserving stritly the energyF he min motivtion ws to e le to ount for soft proesses s well s hrd proesses in the sme glol formlismD to hve omplete desription of ny type of hdroni ollisionF he fq is theory exlusive to iyD hene one of the key ingredients whih mke this iq one of its kindF SS grei QF ri iy iix qixiey yne n see in pigure QFQ digrmmti representtion of AEA ollision in the fqF sn this digrmD the thik lue lines nd lue irles represent nuleons of eh olliding ion A nd BD in the initil stte on the left nd in the (nl stte on the rightF ell the tiny lue lines strting from the nuleons represent prtonsD tht either prtiipte to the ollision vi the exhnge of omerons @drwn with vertil mgent linesAD or re simply remnntsF xote tht in this frmeworkD the omerons re di'erent ojets thn in the q introdued in the lst susetionD where the nuleon is not ssumed to hve ny internl strutureF his digrm gives ler piture of the ws nture of the fqD where ll the intertion represented re onsidered to hppen instntneouslyF he energy onservtion is tken into ount y ensuring tht the sum of energy frtions rried out y ll prtons from eh nuleon is equl to one X

x i + x remn = 1D for oth nuleiF

G sof t , G val-val , G sea-sea , G val-sea and G sea-val [284].
sn the frme of the fqD the omerons re treted di'erently depending on the virtulity sle of the prtons involved in the underlying sttering it represents pheE nomenologillyF here re onsequently (ve di'erent kinds of omeronsD represented shemtilly in pigure QFRD sed on three di'erent types of ontriutionsX E Soft contributions: they orrespond to lowEenergy stteringsD where the prtons involved hve virtulity Q 2 < Q 2 0 D tking Q 2 0 ≈ 1 qeF feing nonEperturtiveD the orresponding pro(le funtion G sof t nnot e lulted from (rst priniples nd hs to e prmetrisedD done here in similr wy s in the qF E Hard contributions: they orrespond to highEenergy proessesD i.e. proesses involving prtons with virtulities Q 2 > Q 2 0 Y heneD it only pplies to interE tion etween vlene qurksF rereD the initil prtons will go through suessive perturtive rditions y inresing their virtulityD until rehing the 2 → 2 prton sttering @the soElled forn proessA t the enter of the prton ldderD where the virtulity is the highestF he orresponding pro(le funtion G val-val n then e lulted from perturtive quntum hromodynmis @pghAD using the hqve eqution PVW to model the virtulity evolution of the prtonsX

d dQ 2 q(x, Q 2 ) G(x, Q 2 ) = α s (Q 2 ) 2π 1 x dz z P qq ( x z ) P qg ( x z ) P gq ( x z ) P gg ( x z ) q(z, Q 2 ) G(z, Q 2 ) , @QFQFUA
with olour indies not shown hereF he funtions q(x, Q 2 ) nd G(x, Q 2 ) re reE spetively qurk nd gluons hpsD whih re not inputs ut lulted within the theoryF P ij (z) re the splitting funtionsD i.e. proility tht qurkGgluon i with initil momentum frtion x splits into qurkGgluon j with (nl momentum frtion z plus nother qurkGgluon rrying momentum frtion x -zF ST QFQF riyisgev pewi yp iy E Semi-hard contributions: they orrespond to ll proesses initited y t lest one se qurk or gluonD thus with virtulity Q 2 < Q 2 0 D ut with virtulity whih evolves to vlues high enough to enle perturtive lultion leding to entrl forn proessF uh ontriutions re represented y the pro(les funtions G sea-sea D G sea-val nd G val-sea D nd ontin therefore oth soft nd hrd prtsF sn hdronEhdron stteringD the totl pro(le funtion G h 1 h 2 1P is then sum of ll the ontriutions from eh oneEomeronEexhnge prtoni stteringF sn ddition to the di'erent possile strutures of omeronsD nonEexpliit in pigure QFQD the ltter ones n e either unut or utD s respetively represented y full nd dshed mgent linesF he ut omerons represent the inelsti stterings nd n e ssimilted to open prton lddersD s shown in pigure QFSF hey re used for prtile produtionD nd ontriute to the totl rossEsetion formul @QFQFVA with positive vlue of their orresponding pro(le funtionsF he unut omeronsD whih represent the inelsti stteringsD or virtul prton emissionsD re very importnt in the frmework euse they ring interferene term in the rossEsetion lultion s they ontriute with negtive vlues of their orresponding pro(le funtionsF of the proess given y the fq is proportionl to sum over the nuleons of terms identil to the following simpli(ed formulD integrted then over d 2 bD sed on equtions @PFTSA nd @PFTTA in PVRX

σ AB tot (s) ∝ cut c c i=1 d 2 b i c i=1 dx + i .dx - i × 1 c! c i=1 G(x + i , x - i , s, b i ) × uncut u u j=1 d 2 b j u j=1 dx + j .dx - j ×    1 u! u j=1 -G(x + j , x - j , s, b j )    . @QFQFVA
sn this equtionD b refer to the impt prmeter etween two interting prtonsD x ± = (x 0 ± x 3 )/ √ 2 re the light one momentum frtion of prtons from projetile @+A nd trget@-AD s the wndelstm vrile referring to the totl energy of the olE lisionD nd c @respetively uA is the totl numer of ut @respetively unutA omerons involved in the onsidered on(gurtionF his importnt formul enles to lulte esily inelstiD elsti or inlusive rossEsetionsD y onsidering spei( on(gurtion of omeronsD wht is one of the strongest points of the fqF SU grei QF ri iy iix qixiey his susetion hve exposed the min ingredients of the fqD suessful ws pproh whih trets energy shring nd prtile prodution in onsistent wyD y inluding oth soft nd hrd sttering treted with pgh lultionsF st n lso e pplied to e + Ee -nnihiltionD using the string model inherited from ix PSTD llowing then to test the hdronistion proedure @whih will e introdued in the next susetionAD nd to eEp stteringD in order to test the semiEhrd omeron strutureF ell the detils out the developments of the formule presented in this setionD the demonE strtions of the equ nelltions leding to rossEsetion ftoristion for the di'erent types of ollisions nd more n e found in PVRF he fq su'ers nonetheless from limittionsD the most ovious one eing due to the ssumption of instntneous intertionsF st is y onsequene only pplile for highEenergy ollisionsD when the longitudinl size of the olliding hdrons is ontrted enough so tht ll intertions do hppen t the sme timeF es simple illustrtionD mking the resonle onjeture tht initil prtons ould intert more thn one if the olliding hdrons were thiker thn HFS fmD one n estimte tht the relevne of the model strts to e questionle round energies down to ∼ 25 qeGe for rsgsD or ∼ 5 qe for pEp ollisionsF his result is otined using simple reltions from speil reltivityD i.e. E = γm 0 c 2 nd γ = 2R/0.5fmD with the liquid drop model formul R = 1.2fm × A 1/3 to lulte the rdius of hevy ion with A = 200F

String Model

enother very importnt feture of the iy event genertor is the string modelD phenomenologil pproh developed to tret hdronistion proedureF es lredy mentioned in susetion IFPFPD the olour on(nement nnot e treted dynmilly with ghEsed methods Y one needs nevertheless to mke link etween the prtons disussed so frD nd the hdrons oserved in detetorsF his prolem hs een (rst treted in PWPD PWQD y ssuming tht the strong olour (eld etween qurks n e modeled y reltivisti stringF uh string is oneE dimensionl ojetD whih trjetory representing surfe in winkowski spe n e desried y fourEvetor x with two prmeters σ nd τ D representing respetively spE til oordinte long the string nd proper timeF reneD requiring vorentz invrine nd guge invrine on the dynmis of this stringD one gets the following vgrngin from whih ll the dynmis n e derived using the iulerEvgrnge equtionX

L = -κ (x ′ ẋ) 2 -x ′2 ẋ2 , @QFQFWA
where x ′ nd ẋ re the sptil nd time derivtives of x PSTF he prmeter κ is the string tensionD whih vlue is tken s ∼ 1 qeGfmD s usully tken to desrie the tension of the strong olour (eld in most models F Figure 3.6: A kinky string formed by a q-q pair, created after an e + -e -annihilation, with an emitted transverse gluon [294].

SV QFRF qixiesyx yp ex iix sx iy sn iyD the string is identi(ed s qEq pir of the sme )vour linked y gluonsD forming thus prton hin qEgEFFFEgEqF hen simply formed of qEq pirD the string is purely longitudinl ojetD while gluons n dd trnsverse dimension to it vi trnsverse kinksF uh strings re referred to s 4kinky strings4D s shown in pigure QFT in the se of e + Ee -nnihiltionF es the prtons hve some initil momentD the string will e strethed s they exE pndD wht will led to inrese its potentil energy due to its tensionF his mimis the liner potentil of the strong intertion etween qurks t reltively lrge distnes @typilly few fmAF et some pointD it is fvorle to use this energy to produe new qEq pirD with the sme )vour to not violte its onservtionD rther thn strething even more the stringF hus the string will rek into two segmentsD whih will ontinue to evolve nd frgment in turnD reduing their tension eh time they will splitF hey will do so until they nnot rek nymoreX they n then e identi(ed s hdronsD s shown in pigure QFUF his proess is often referred to s the 4hwinger mehnism4 in the literture PWSF sn order to ount for ryon produtionD it is lso possile to rete q i q j Eq i qj pirs t reking pointD i, j eing the )vour indiesD with lower proility thn for qEq pir thoughF elthough ny qurk )vour n ompose the extremities of stringD only the light )vours uD d nd s n e produed t the reking pointsD for ovious kinemti resons @the mss of cEc pir eing of the order of ∼ 3 qeD ompred to sEs pir with mss of ∼ 200 weAF he reking points long the string re generted following soElled re lwD sed on PSVF he proility dP for string to rek t given point (σ, τ ) is similr to the exponentil dey lw of unstle prtilesX

dP = λ dA = λ (x ′ ẋ) 2 -x ′2 ẋ2 dσdτ, @QFQFIHA
where λ is the dey onstntF reneD the surfe desried y the string in the (⃗ σ, ⃗ τ ) is rndomly divided into suEpiees of re dAD nd the proility to rek the stringD in other words tht the string long the line delimiting this re is proportionl to the size of this reF sn this respetD this string model is di'erent from the vund string modelD whih uses frgmenttion funtions PWTF he foundtions of the full string model formlism used in iy n e found in PSTD with further developments given in PWUF 3.4 Generation of an event in EPOS sn this setionD the omplete proedure whih is pplied to simulte n event for hdroni ollision with iy R will e desriedD independently of the nture of the projetile nd the trgetF st will therefore mke the link etween ll the importnt ingreE dients presented previouslyD ehoing to the generl piture of rsg simultion desried in (gure QFI st will lso summrise ll the di'erent fetures implemented stepEyEstep SW grei QF ri iy iix qixiey over time in the modelD s presented in setion QFPD giving so n updted piture of the event genertion in iyF he initil intertions etween olliding hdrons re treted using the fq @preE sented in susetion QFQFQAD vi the genertion of rndom on(gurtion of omerons nd the ssoited rossEsetion lultionsF he ut omerons produe this wy n initil distriution of prtonsD whih will e used s strting point for the event evolutionF revy qurks re not present in the initil olliding hdronsD nd n only e produed in the prton ldders t this erly stge of the ollisionX either in speElike sdesD timeElike sdes or in forn proess @2 → 2 tree level digrmAD s drwn in pigure QFVF hey re treted with their nonEvnishing physil msses @tken s m c = 1.3 qeD m b = 4.2 qeAD wht will hve n impt on splitting onditions in the prton ldder kinemtis PWIF Thick blue lines represent nucleons, while thin blue lines are drawn for partons [291].

he inrese of nonEliner e'ets with the energyD i.e. reEintertions of ldder prE tons with projetile or trget due to gluon sturtionD is tken into ount vi hnge of the onstnt Q 0 previously introduedF ih omeron is now getting ustomised dynmil sturtion sle Q s (x P E , N conn ) determining the trnsition from hrd to soft tretment of the prton ldderD whih depends on the omeron energy frtion x P E nd on the numer of other unut omerons onneted to the sme nuleons N conn PTWF he initil prtons produed in the ldders re then mpped to stringsD whih re lwys strting from @ntiAqurks or @ntiAdiqurks from the projetile or trget remE nntsY the kinemtis of those prtons provide initil onditions for the string dynmisF elsoD one omeron orresponds to t lest two stringsD so tht it remins olourEneutrl ojetF roweverD in AEA or even highEmultipliity pEp ollisionsD s multiple intertions hppen t the sme timeD mny strings n e superimposed on eh otherD s repreE sented in pigure QFWF sn this situtionD the strings might not e le to evolve nd dey independently from eh othersY for tht resonD oreEoron proedure is pplied t some erly time of the evolution τ 0 PTRD whih is prmeter or the modelF st onsists of hekingD where the lol string density ρ is eyond ertin ritil vlue ρ 0 D if the TH QFRF qixiesyx yp ex iix sx iy string segments hve enough trnsverse energy to espeX

p new T = p T -f E loss γ ρ dL.
@QFRFIA sn this formulD p T is the initil trnsverse momentum of the onsidered segmentD f E loss is simply prmetrised onstnt depending on p T D nd γ is the hypothetil trjetory of the segment PTUF henD if the omputed p new T vlue is positiveD the string segment will espe nd e prt of the 4oron4D where it will ontinue its evolution nd eventully frgment s desried in susetion QFQFRF en importnt feture in iy is the ft tht trget nd projetile remnnts re left o'EshellD nd will thus ontriute to prtile prodution t lrge rpidity s prt of the oron PTPF Figure 3.9: Schematic view of a collision with many strings (in red) exchanged between projectile and target remnants (in blue) : the dense part will compose the core, while the high-p T segments will escape in the corona [294].

fy oppositionD if segment doesn9t hve enough energy to espeD it will remin in the soElled 4ore4F sn order to reprodue the )uidElike ehviour of the qD the ore will then evolve using visous reltivisti hydrodynmisF uh hydrodynmi tretment n e used euse in this seD the men free pth of prtiles λ M F P is smll ompred to the hydrodynmi lengthsle L hydro = (∂ µ u µ ) -1 @here the 4rel4 prtiles onsidered re @ntiAqurksAF he ltter n e interpreted s the length on whih the system is onsidered homogeneousD u µ eing is the veloity fourEvetorF he energyEmomentum tensor T µν nd )vour )ow vetor N µ q re then determined from the string segments following the following formule PTQX

T µν (x) = i δp µ i δp ν i δp 0 i g(x -x i ) , N µ q (x) = i δp µ i δp 0 i q i g(x -x i ), @QFRFPA
where δp re the fourEmoment of the string segmentsD q i their netE)vour ontent @either qurk )voursD or hrges like B, Q nd SAD nd g(...) is qussin smoothing kernel with trnsverse width of HFPS fmF his mpping is done y ssuming fst thermliE stion of the dense mediumD whih is strong ssumption mde in iy PTUF he evolution of the ore is hieved eventEyEevent with the vrvvi ode PWVD whih resolves the equtions of reltivisti visous hydrodynmis ∂ ν T µν = 0 nd ∂ ν N ν q = 0D using the ssrelEtewrt pproh PWWF his stge of the ollision is wht is generlly TI grei QF ri iy iix qixiey referred to s 4rnsport theory4D s shown in (gure QFIF he equtions of reltivisE ti hydrodynmis re expressing the lw of energyEmomentum onservtion nd )vour onservtionD nd re generl to oth idel nd visous reltivisti hydrodynmisF rowE everD in the presene of visous e'ets @expressed vi nonEzero vlue of sher visosity η/s = 0.08AD the previous tensor nd vetor hve the expression PTUX

T µν = ϵu µ u ν -(p + Π)∆ µν + π µν , @QFRFQA N µ q = n q u µ + V µ q , @QFRFRA
where ϵ nd p re respetively the energy density nd the equilirium pressureD π µν nd Π the sher stress tensor nd ulk pressureD V µ q re the qurk hrge di'usion urrentsDn q the qurk densities nd ∆ µν = g µν -u µ u ν the projetor orthogonl to u µ F sn iyD there re two implemented hoies of io for the hydrodynmi tretment of the oreF he (rst oneD 4rossEover 8 Q )vour onservtion4 @QpAD inludes rossEover trnsition etween hdron resonne gs nd n idel qD nd is prmetrised to mth with lgh lultions t vnishing hemil potentils @detiled explntions in PTUAF he seond oneD proposed y the Beam Energy Scan Theory @fiA ollortionD inludes in ddition of the rossEover trnsition t low µ B 1 st order phse trnsition etween hdroni gs nd q with giD whih oordintes re left s free prmeters PIVF yne the ore hs expndedD the regions whih hve suessively een diluted down to n energy density ϵ H = 0.57 qeGfm 3 PUH will hdronise long given hypersurfe of onstnt energy densityF et this levelD there re gin two possiilities onerning the formlism hosen to hieve itF he (rst one is the gooperEprye proedure PTTD lso referred to s 4therml model4D whih mounts to generte momentum distriution dN i /d 3 p of prtiles i t the hypersurfe element dΣ µ following the reltionX

E dN i d 3 p = Σ dΣ µ p µ × f i (p µ u µ , T, µ i ) @QFRFSA
with f i (p µ u µ , T, µ i ) the lol permiEhir or foseEiinstein distriutionD depending on the nture of the onsidered prtiles i nd on the lol temperture nd ssoited hemil potentilsF he numer of prtiles N i is generted here following oisson distriution in the qg ensemleD s detiled in PTSF he seond hdronistion proess ville is mirononil pprohD in whih prtiles re produed from the dey of )uid ells with e'etive volume nd mss de(ned respetively y PWRX

V = Σ u µ dΣ µ , M = Σ T µν dΣ µ T µν dΣ ν . @QFRFTA
henD the proility to produe nEhdrons distriution omposed of n α prtiles from eh speie α is givenD in the rest frme of the onsidered ellD y PUIX

dP = V n (2πℏ) 3n × n i=1 g i × α 1 n α ! × n i=1 d 3 p i × δ E - E i × δ ||⃗ p i || × A δ Q A - q A i
. @QFRFUA he hir funtions re here to ensure strit onservtion of energyD momentum nd )vour urrents @A indies referring here to onserved hrges B, Q, SD with Q A the totl netEhrge A of the ell nd q A i the hrge A rried y prtile iAF he strong point of this pproh is tht it onverges to the qg limit for lrge e'etive msses M PUID nd is therefore now the defult one used in iy RF woreoverD its use is of prtiulr TP QFSF yftigsi yp ri ris importne in the frme of the study of )ututions presented lter in hpter SD s it ensures oth glol nd lol onservtion of hrgesF et this stgeD hdrons formed from oth ore nd oron re still in dense gseous phse nd n intert mong eh otherF he hdroni sdesD or 4hdroni restterE ings4 from (gure QFID re hene simulted with the Ultra-relativistic Quantum Molecular Dynamics @rwhA mirosopi trnsport model PRTD PRUD where prtiles go through either elsti or inelsti stteringsF he rossEsetions ssoited to eh retion vilE le in rwh re oming from experimentl mesurementsD or lulted vi the Additive Quark Model @ewA QHHD QHIF hese proesses will lst until the omplete kineti freezeEout of the systemD when ll the retions eseD nd the (nlEstte hdrons will ontinue their free stremingD eventully undergoing some lte wek deysF he event is then ompletely simultedF hen generting events with iy in order to ompre simultions with experimenE tl dtD the nlyses re generlly performed diretly on the list of (nlEstte prtilesD without ny further simultion of detetor e'etsF he min reson is tht the e'ort of estimting the unertinties due to trk reonstrutionD prtile identi(tion nd detetor e'ets is generlly mde y experimentlistsD s eing intrinsi to their nlyE sis proedureY suh e'ets re tken into ount in the systemti unertinties of the presented resultsF his wy of proeeding is generlly eptle ut still shows some limittionsD notly regrding the topi of entrlity de(nitionD s it will e disussed in setion RFPF 3.5 Objectives of the thesis es onlusion to these three hpters whih settled the physil ontext nd introE dued my min working toolD s will desrie in this setion the min gols of this thesisF pousing on the tehnil spets relted to the puli relese of iy R in the (rst pleD s will then expose my reserh plns onerning the study of netEhrge umuE lntsD minly sed on experimentl results of the e ollortion from PII nd on some relted investigtion y the uthors of PQRF 3.5.1 Towards the release of EPOS 4 es lredy mentioned severl times in this hpterD new iy version hs een under development in the pst few yersD nmed iy R PTWD PUIF st hs led to relese pulily stle version of this iqD ontining ll the min ingredients ited previouslyD inluding the most reent improvements on the theory nd new fetures PTVF sn this respetD n importnt work hs een hieved on the struture of the odeD its usility nd onnetion to other toolsD in order to mke it esier to hndle for ny userF he question of dt mngement nd nlysis is of prtiulr importneD s omE pring the results of simulted events to experimentl dt is the fundmentl purpose of iqsF st is not only essentil for the developerD who hs to ensure tht its model n reprodue experimentl oservles in oth qulittive nd quntittive fshionD ut lso for the userD who needs to e le to exploit the results of the simultions with essile toolsF TQ grei QF ri iy iix qixiey reneD hving s primry ojetive the vlidtion proess of iy R in sightD ut knowing it would e ene(il for users too one relesedD s hve een responsile for developing n interfe etween iy nd the nlysis 8 omprison tool ivetF uh tsk implied dding new output dt formt to the ode s (rst stepD nd to go even further y inserting in the iy nlysis frmework systemtistion of ivet9s usgeF st ws oviously ompnied with the writing of orresponding doumenttionD onerning oth userErelted nd internl developmentsD whih is ville online PTVF his (rst projet will e presented in detil in hpter RF roweverD the vlidtion proess of generlEpurpose iq requires to ompre its results to lrge set of experiE mentl dtD from mny di'erent systems nd energiesD in order to djust the prmeters of the underlying model@sAF nfortuntelyD the numer of nlyses nd orresponding dt ville in ivet is limitedD espeilly out rsgs whih is our min interest with iyF es onsequeneD s hve lso een responsile to hek nd rewrite preexisting nlysesD s well s olleting more reent dt nd write the orresponding nlysesD for the fi progrm energiesF he ide ws to hve very omplete set of nlyses redyD to ompre iy results with dt from lower nd lower energiesD nd see how resonly n it e pplied to this energy rnge despite the limittions of the fq disussed t the end of the susetion QFQFQF win results from this energy snD using minly onventionl nlyses ut lso the new iy+ivet frmeworkD will e presented in hpter SF pinllyD nother physisErelted ut rther tehnil prolem whih s hve een in hrge to solve hs to do with some inonsistenies found in the de(nition list of dey rnhing rtios in the (le KWt/idky5.dtF por dozen of prtilesD minly mesons for whih there re not mny informtion in IRD the sum of dey rnhing rtios ws found to e signi(ntly di'erent from I Y more thn VS7 of rnhing rtio ws even lking for some of them in prtiulrF hese lks of de(nition for dey possiilities would oviously produeD t the estD deys with inonsistent proportions of outgoing prtilesD ut ould t worst led to unexpeted ehviours of the ode in the mngement of deysF elthough the prtiles involved re not produed mssively in ollisionsD it is importnt to keep onsistent piture on ll physil spets for generlEpurpose iqF reneD s hve updted the list of dey hnnels for the prolemti prtilesD onsidering only hnnels with t most (ve outgoing prtiles s iy is not tehnilly designed to mnge deys with more produtsF s hve espeilly tken into ount the gleshE qordn oe0ients in the lultion of rnhing rtios for hrge symmetri hnnelsF por qurkoni with lks of informtion in IRD s hve followed the ythi method y ompleting the rtios up to I vi X → g g dey hnnelsD repling gluons y qEq pirs s iy does not hve ny routine to hdronise gluons in the (nl stteF s used this osion to reorgnise ompletely the (le y sorting it in sending order of prtile shsD for redilityD nd orret some doule delrtions disovered during the opertionF 3.5.2 Towards the study of net-charge cumulants sing the events we generted for the fi energies s prt of the vlidtion proess of iy RD s will fous my physil study on the 2 nd order umulnts of netEhrges TR QFSF yftigsi yp ri ris B, Q nd S nd orresponding netEprtiles proxies pD π nd K in euEeu ollisionsF his work is initilly sed on two pulitionsD oth lredy introdued in susetion PFQFQF es reminderD the (rst one ontins mesurements of @oAvrines nd their rtios for prtile netEumulnts mde y the e ollortion PIIF he seond one is study on the rekdown of hdroni ontriution to the netEhrge umulntsD with proposition of enhned proxy rtios ompred to the ones used y e PQRF he (rst steps of my study will onsist of looking t the importne of the soE lled gfg when lulting @oAvrines of netEprtile numer s funtion of the numer of N part diretlyD s rossEhek with some previous studiesF sn order to ridge gp etween the experimentl results nd theoretil studies led on the topi in reent yersD s will use iy to mesure the 2 nd order umulnts of onserved netEhrgesD nd of netEmultipliities for hdroni speies of interest X π ± D K ± D pD pD ΛD ΛD Ξ -D Ξ + D Ω -nd Ω + F sing n event genertor enles indeed to get rid of identi(tion prolemsD whether for the detetion neutrl prtiles or the reonE strution of shortElived prtilesF hnks to this ilityD it llows to lulte diretly the )ututions of onserved hrges rried y hdrons in given kinemti regionF reneD s will onfront the results otined with e proxies ginst the enE hned proxies from PQRD presented in susetion PFQFQF s will exmine how they di'er from eh otherD s well s their respetive hnge with the vrition of the ollision energyD ompred to the umulnts of orresponding netEhrgesF enother strong point of working with n event genertor is tht one n hve ess to the whole history of the events simultedF ith this fetureD nd more prtiulrly the modulr oneption of iyD it is possile to investigte the impt of the di'erent stges of the ollision on (nlEstte oservlesF sn this regrdD s will try to quntify the impt of the hdroni sdes on the oservles of interest s well s on some of the enhned proxiesD s motivted in susetion PFQFQF st will e hieved y ompring their mesurement from simuE ltionsD efore nd fter this (nl stge of the ollisionD modeled vi rwh in iyF purthermoreD one of the peulirities of iy is the use of oreEoron proedure when simulting the ollisionsD s desried in setion QFRF sn this pitureD the ore orresponds to nerly perfet )uid whih emultes the ehviour of q dropletD while the oron orrespond to pure hdroni stge modeled with the string pprohF king dvntge of this fetureD s will estimte for ll the oservle mentioned previously the proportion of the signl originting from the oreD s it is the prt of the system whih would go through phse trnsition nd thus imprint potentil therml )ututionsF he results otined from ll the previous points will e presented nd disussed in the hpter SF TS grei QF ri iy iix qixiey fefore moving onD let still lrify lredy why not using the fi eqution of stte ontining giD newly implemented in iyD to investigte diretly the e'ets of ritilityF he issue is tht onventionl reltivisti visous hydrodynmis pprohesD suh s the one used in iy PWVD re ll out verged quntities t mesosopi sle @i.e. intermediry etween mirosopi nd mrosopiAF uh desription is only relevnt when )ututions of the quntities in question re negligile in omprison to their vergeF gonsequentlyD suh frmeworks re not suited to desrie the rise of imporE tnt therml )ututions used y the presene of giD nd doing so would require to inlude stohsti terms to the dynmil evolution equtionsD wht is urrently hlE lenging prolem in rsgs simultions PPPF sn ftD (rst study hs lredy een mde y inorporting the fi eqution of stte into iyD nd ompring then simultions with nd without giF st hs shown no signi(nt di'erenes in si oservles suh s p T spetr nor in the results of umulnt nlysisD even when vrying the lotion of the giD wht tends to on(rm the previous rgument PUHD QHPF TT CHAPTER 4

TECHNICAL DEVELOPMENTS FOR EPOS 4 ith the puli relese of ny new version of n iqD omes the neessry tsk to (x properly ll the free prmeters of the underlying modelsF es exmplesD we n ite for iy the prmeters neessry to desrie the soft omerons mplitudes in the fE q @disussed in susetion QFQFQAD or the ones used to de(ne the sturtion sle of the semiEhrd omeronsF por generlEpurpose iqs like iyD this proess n however eome omplitedD euse they generlly ontin mny free prmetersF woreoverD heking tht the urrent prmetristion work well mens running simultion for mny di'erent systems t mny di'erent energiesD the im eing to to see how good prtiE le prodution n e reproduedD y ompring the results of simultion with severl oservles mesured experimentllyF por iy in prtiulrD we tlk out ollisions from rsg to vrg energiesD i.e. from few dozens of qe up to thousnds of e in the enterEofEmssD for ll systems @pEp D pEA or AEA AF sn order to help in this opertionD ivet is the idel tool y esseneD euse of its purpose to utomtise omprison etween iqs nd experimentl dtF gonsequentlyD s will explin in the present hpter why nd how s hve dpted iy R to mke it omptile with ivetD nd espeilly why nd how s even integrted the ltter in the nlysis frmework of iy to utomtise its opertionF o this endD s will introdue ivet in setion RFID desrie how it works nd motivte why it is useful not only for usD iq developersD ut lso for the usersF s will give some tehnil explntions on the funtioning of iy R in setion RFPD neessry to desrie then in setion RFQ ll the tehnil work s hieved to inlude ivet in the iy R nlysis systemF pinllyD setion RFR will summrise the work presented eforehnd y explining how to e'etively run iy with ivetF feyond the neessity to develop n nlysis tool whih is useful for the forementioned tsksD this new funtionlity will then e useful for the study presented in hpter SD in order to ensure tht iy reprodues properly prtile distriutions in the simulted events usedF st hs lso een shown to e useful in studying gfi on the umulnts of netEprtile multipliities whih re studied thenF 4.1 RIVET Robust Independent Validation of Experiments and Theory @ivetA is toolkit mde of olletion of lirriesD developed for over dede now for wg event genertors vlidtion nd tuning QHQF he min philosophy ehind ivet is to o'er n esyE toEhndleD utomti nd stndrdised tool for nlysis nd dt omprisonF snitilly reted to study minly w physis nd hps in e + Ee -nd pEp ollisionsD it hs developed over wide vriety of pplitions sineF eentlyD new fetures hve notly een implemented in order to filitte the use of hevyEion nlyses QHRD expnding thus its rnge of ppliilityF feing the min themti of reserh for iyD s will hene explin in this setion the motives of using siD fter rief presenttion of its struture nd tul funtioningF 4.1.1 General presentation ivet is priniplly sed on g++ lirries nd ython progrmming nd ommnd interfesF st omes with olletion of preEenoded nd funtionl nlysesD eh nlE ysis orresponding to one given pulitionF i'etivelyD the user hs to provide the dt to nlyse @generlly from iq simultionsA in spei( (les written in the stndrd of High-energy physics Monte-Carlo @repMCA pkgeF sn suh (lesD the history of eh event is reorded under text formtD with informtion on em nd projetileD verties nd prtiles produedD etF @more detils will e given in susetion RFQFIAF he user n TV RFIF si then run the nlysis of their hoie on itD wht will reprodue the distriutions shown in the orresponding pulitionD ut sed on the provided dtF pinllyD the user n disply the results in plotsD where they will e ompred to the tul experimentl dt from the pulitionD s the inning used in the nlyses is sed on the ltter onesF reneD eh nlysis pkge omes with R di'erent (lesD ll nmed the sme wy @e.g. 4ANALYSIS_NAME4A ut with di'erent extensionsX ANALYSIS_NAME.cc ontins the nlysis itself to e run on iq dtD writE ten in g++ with the help of ivet dedited lirriesY ANALYSIS_NAME.yoda ontins the experimentl dt from the (gures shown in the pulition @for simpliityD this (le is synhronised with the Hepht weE site 1 when dt re ville on itAY ANALYSIS_NAME.plot ontins the informtion of the plots from whih exE perimentl dt plns to e ompred to @xes lels nd slesD title nd more if neessryAY ANALYSIS_NAME.info ontins generl informtion on the ivet nlysisD suh s its uthor@sAD the pulition of refereneD etF yne of the strengths of ivet is its ese of use X very few ommnds re neessry to run nlyses nd disply the resultsD s will e presented in the following prgrphsF he im is not to give omplete nd exhustive explntions on how to run ivetD ut to show onretely the few ommnds tht will e useful in the utomtion of ivet useD desried in susetion RFQFPF o (nd more doumenttionD referene pulitionsD list of ville nlyses or even tutorilsD one n visit the ivet wesite 2 F sn the stndrd se of previously ville nlysis 4ANALYSIS_NAME4D the user n simply run it on the events reorded from simultions @stored in (le whih will e lled DATA.hepmcAD speifying if neessry nme for the output (le with the )g 4-o4 @for this exmple ANALYSIS_EG.yodaAX $> rivet DATA.hepmc -a ANALYSIS_NAME -o ANALYSIS_EG.yoda he results of the nlysis re stored in .yoda extension (leD Yet more Objects for Data Analysis @ODAA eing pkge of lsses delivered with ivetD used to mnge histogrmmingF henD in order to disply the resultsD the user n run the following ommnd X $> rivet-mkhtml ANALYSIS_EG.yoda -o ANALYSIS whih will produe one dt (le for eh histogrm of the nlysisD nd disply the plots with the results of the nlysis ompred to the orresponding experimentl results under hp nd xq formtsF st willD in dditionD generte plot we pge whih gther ll these plotsF he dt (les thus reted @with .dat extensionsA ontin results s (x, y) vluesD plus the ssoited unertintiesD unlike the ODA (le resulting from the nlE ysesD whih ontin the omplete informtion on the (lling of histogrms @more detils will e given in susetion RFQFPAF hen deling with sustntil numers of events @silly millionsD when trying to hve similr sttistis thn for experimentl resultsAD the user might wnt to run grei RF igrxsgev hiivywix py iy R the nlysis in prllel on severl repMC (lesF here isD in this seD one dditionl ommnd to merge the multiple (les otined from the sme nlysis @ndD y extensionD the results they ontin for di'erent sets of eventsA into unique (le X $> rivet-merge ANALYSIS_EG-1.yoda ANALYSIS_EG-2.yoda [...] -o ANALYSIS_EG.yoda e summry of how ivet worksD linking ommnds nd (les from the di'erent steps ited previously with the orresponding lssesD is shown in pigure RFIF vst ut not lest importnt pointD for user interested into hevyEion nlysesD is the neessity to provide entrlity lirtion in order to mke the nlysis run suessfully @s for some pEp nlyses deling with highEmultipliity eventsAF he user thus hs to run the lirtion nlysis on the eventsD nd to provide the resulting distriutions @stored in (le lled CALIB.yoda for this exmpleA s n input for the desired hevyEion nlysisD preeded y 4-p4 )gX $> rivet DATA.hepmc -a ANALYSIS_NAME:cent=GEN -p CALIB.yoda -o ANALYSIS_EG.yoda yne shll notie there the omplementry instrution indited fter the nlysis nmeD i.e. 4:cent=GEN4F his instrution indites in whih wy the lirtion hs to e doneX 4cent=EXP4 to de(ne entrlity lsses sed on provided experimentl multipliity distriution @when villeAD s desried in setion PFPY 4cent=GEN4 to de(ne entrlity lsses sed on generted multipliity distriutionY 4cent=IMP4 to de(ne entrlity lsses sed on the generted impt prmeter distriutionF UH RFIF si sn light of these explntionsD one might now understnd the ruil role tht is plying ivet in the physis of ollidersD y o'ering dedited omprison toolF st is indeed of interest for the theoretil ommunity nd espeilly iq developersD s lredy disussedD euse it propose simple wy to ompre the results of their simultions to experimentl dt for the vlidtion of the modelsF st n lso e used s wy to dilog with experimentl ollortions in need of preditions for their pulitionsD s it is ustomry when pulishing new mesurements resultsF he ollortions ould for instne provide funtionl ivet nlysis to developers of the iqs they wnt preditions fromF hile inning is usully utomtilly sed on the experimentl dt distriutionsD ivet o'ers the possiility to de(ne ustomised inning for histogrms used in nlyses wht llows in suh situtions to deliver the nlysis without the exE perimentl dt to e pulishedD hene preserving their on(dentilityF yn purely experimentl levelD nd dditionlly to the powerful toolkit it o'ers to perform nlysesD ivet even o'ers for experimentl ollortions good lterntive to sveD nd minE tin the usility of their nlysesF pinllyD ivet is eing developed y dedited tem of sientists from vrious (elds of riD who know the di'erent needs proper to eh (eldF feing esily rehle vi the ivet qitv projet 3 D they re open to ny suggestions to improve the toolkit nd roden its possiilitiesF roweverD they highly rely on ontriutions from outside people to rry out the tedious tsk of expnding the nlysis tlogueF ivet is thus tool developed for the ri ommunityD ut whih lso needs ontriutions from ommunity to keep growing nd to o'er fetures nswering its needsF 4.1.2 The benets for EPOS elthough iy ontins its own eventEyEevent nlysis system integrted in the ode itselfD whih will e introdued in susetion RFPFQD there re severl dvntges to dpt it for ivet9s useF pirst of llD there re ler ene(ts for usD iy developersF fy o'ering lrge tlogue of nlysesD it n e used to test our iq during the vlidtion phse s sid eforeF fut more importntlyD it frees us from hving to write the nlyses y ourselvesD espeilly the elorted ones like )ow nlysesF iven though suh things n e done in iy nlysis frmeworkD we ensure tht the nlysis is mde extly s it should when using ivetF e don9t hve to tke re then out ll tiny detils on the methods nd kinemti uts ppliedD whih re not lwys lerly expliited in the pulitionsF here re lso multiple ene(ts of dpting iy to ivet for usersF rimrilyD it o'ers n esy wy to ompre the simulted events to experimentl dt without hving to hndle iy nlysis frmework or yyD for whih iy n lso produe omptile event reordsF ivet enle users either to run some ville nlysesD or to write their own nlyses quite esilyF eondlyD the new output formt neessry for suh omptiilityD the repMC (lesD is in simple text formt whih is esily redleF st ould even e used diretly to mke quik nlyses vi simple sriptsD in whtever lngugeD for pedgogil purposesF pinllyD we hope tht proposing suh omptiility will enourge experimentlists to systemtilly sumit their nlyses to ivet when pulishing new resultsD for ll the resons exposed t the end of the lst setionF 3 https://gitlab.com/hepcedar/rivet UI grei RF igrxsgev hiivywix py iy R xeverthelessD ivet su'ers from limittions euse of its dependeny on ontriuE tions from user to sumit nlysesF por instneD the ft tht hevyEion dedited tools were developed only reently n e seen y the smll numer of hevyEion nlyses villeD ompred to nlyses for pEp ollisionsF woreoverD the di'erent experimentl ollortions re not ll equl regrding the overge of their nlyses in ivetF yne n see in pigure RFP tht the overge perentge vry from experiments to experimentsF he numer of ville nlyses is espeilly low for rsg experiments in prtiulrD whih explins why we hd to use iy nlysis system to hek the vlidity of iy R in the energy rnge of the fi progrmF

How EPOS works in practice

rving motivted the resons tht led to integrte ivet in iy nlysis frmeE workD s will now introdue some tehnil elements out iy opertion nd the struE ture of the odeF hese explntions re provided to pprehend how iy worksD nd therefore to understnd how ivet hs een integrtedD s s will present in setion RFQF hey might lso e useful to the reder when the implementtion of the netEumulnts nlysis neessry to the min study of this thesis will e disussed in ppendix gF xeverthelessD only the piees of the ode tht mtters for the following disussions will e introduedD hene not ll detils of the struture nd funtioning of iy will e mentionedF 4.2.1 Structure of the repository s will introdue step y step the di'erent piees of the ode strutureD s displyed in pigure RFQF es onsequeneD s will not repet eh time the omplete pth of the (le s will e itingD onsidering this pigure s referene for the rederF vet me however notie tht the struture of the repositoryD s s will desrie it hereD n e sujet to hnges fter potentil future developments of iy RF he min diretoryD tht s will ll EPOS/ hereD ontins multiple folders ndD mong othersD the sript epos whih is lled to exeute the progrmF he EPOS/src/ folder is of prtiulr importne sine it ontins the soure odeD nd in prtiulr the (le main.cpp whih is the spinl olumn of the progrmD s it lls ll the min UP RFPF ry iy yu sx egsgi funtions nd suroutines of the progrmF he EPOS/src/KW/ folder ontins severl portrn (les with the suroutines omposing the rest of the skeleton of the odeF sn EPOS/src/KWb/ re priniplly stored g++ (les in whih re de(ned the funtions used to mnge the reord of the events in the yy formtD nd onsequently where s will store the equivlent funtions to produe the repMC output (les @see susetion RFQFIAF sn the EPOS/src/KWt/ folder re tulted importnt informtions out physisX the list of de(ned prtiles nd their properties in idt.dtD the de(nitions of ll dey hnnels for eh prtile in idky5.dt @disussed with more detils in ppendix ??AF emong other thingsD it lso ontins ll the entrlity lirtion informtion for eh system t eh simulted energyD in (les lled iclSYSeng.optnsD where 4SYS4 refers to the system simulted nd 4eng4 the energy @e.g. iclAuAu200.optnsAF s will ome k on the ontent of those (les in susetion RFPFPD when disussing the wy we del with entrlity in rsg simultionsF qeD thus lled AuAu200.optnsF he very (rst thing to do is to de(ne the type of system to ollideD s iy n simulte ny type of hdroni systems ut lso e + Ee -nd eEp ollisions s well @see lst prgrph of susetion QFIFIAF yne hving de(ned the nulei to ollideD the energy is set in qeD in the enterEofEmss of nuleon pirF iven though for hdroni systems the prtiles ollided re trditionlly nuleiD iy relly o'ers the possiility to ollide ny hdron like pionsD konsD etF sn the sme wyD iy n not only simulte e + Ee - ollisions ut lso µ + Eµ -onesF en exmple is displyed in ( yne n hoose to tivte or not the di'erent fetures of iy presented in setion QFRD i.e. the oreEoron seprtion with hydrodynmil evolution of the oreD nd the hdroni reEstterings simulted with rwhF sn se the hydrodynmis is tivtedD one n hoose whih io to use for the simultionD etween the two introdued in seE tion QFRF o de(ne the numer of events simulted in the runD one hs to set 4nfull4 nd 4nfreeze4 so tht the totl numer of event generted will e equl to nfull×nfreezeF he 4nfull4 vlue orresponds to the numer of di'erent initil onditions simultedD nd 4nfreeze4 to the numer of hdronistion nd susequent evolution of the system for eh initil evolution simultedF his feture is notly used in the se of simultions using hydrodynmisD whih n e extremely timeEonsuming in term of omputing reE souresF st is thus ustomry to set for instne 4nfull4 to R nd 4nfreeze4 to S for euEeu ollisions simulted with hydrodynmis t √ s N N = 200 qeD mening tht S omplete events re generted out of eh of the R di'erent prior hydrodynmi simuE ltionsF por simultions without hydrodynmisD 4nfreeze4 is generlly left to I thoughF here is lso possiility to speify some prtiles for whih the dey will e lokedD nd tht will then e onsidered s (nlEstte @pA prtiles if produed during the olE lisionD using the 4nodecays4 instrutionF uh possiility llows to pply perfet feedE down orretion to spei( hdroni speies su'ering from wek deysD or to keep trk of shortElived prtiles of interest suh s qurkoniF xote tht the numering sheme for prtile shs in iy is di'erent thn the usul rtile ht qroup @hqA numering sheme IRF iven though the philosophy is the smeD the min di'erene is tht up qurk omes with sh EPOS = 1 nd down qurk with sh EPOS = 2D while eing the ontrry in the hq numering shemeF reneD in the previous exmpleD prtiles for whih the deE y is loked re π 0 @sh EPOS = 110A nd K 0 s @sh EPOS = 20D s PQH is eing used for K 0 AF UR RFPF ry iy yu sx egsgi sn order to mnge the entrlity for rsg simultionsD one n set the vlue of the 4centrality4 vrile in the .optns (le to EI to hve rndom genertion of the vlue of the impt prmeter bF sf set to HD the rndom vlue of b will e generted ensuring t lest one hdroni intertion in the ollision @minimum isAF ytherwiseD one n t lst ssign it to vlue from I to PHD orresponding to S7 sed entrlity lsses going inresingly from the most entrl ollisions @4centrality 14 for HES7 ollisionsA to the most peripherl ones @4centrality 204 for WSEIHH7 ollisionsAF hese entrlity lsses re sed on the impt prmeter distriutionD nd re de(ned in EPOS/src/KWt/icl[...].optns (lesD whih re red vi the 4xinput4 ommnd yne n (nlly run simultions y lling the epos sriptD nd providing s n rguE ment the nme of ny .optns (le @without the extension thoughAD likeX $> epos -root AuAu200 he 4-root4 )g is optionl nd indites to sve the yy (le in whih the events re reordedD s the 4fillTree4()4 instrutions is only used to tivte the reordingF 4.2.3 Using on-the-run analyses es mentioned in the previous setionD iy omes with n 4onEtheErun4 eventEyE event nlysis systemD minly de(ned in portrn suroutines written in EPOS/src/K-W/xan.fF st llows to run nlyses on the simulted events without neessrily hving to store those events in ny output (leD whih is fst nd relly onvenient for develE opers when performing tests with the modelF xeverthelessD there is still possiility to run these nlyses on events preEreorded in yy (lesD s it n e useful to perE form nlyses on some events for seond time @e.g. for entrlity lirtionD disussed erlierAF Writing an analysis in EPOS o use this toolD the nlyses hve to e written diretly in the .optns (leD fter the settings of the events simultedF e simple nlysis is shown here in (gure RFSD used to reE produe p T distriution like the ones whih will e presented in hpter SF ome other exmples re lso ville in the expl [...] US grei RF igrxsgev hiivywix py iy R fetween the 4beginhisto4 nd 4endhisto4 shll e spei(ed ll the hrteristis of the nlysisF sn (rst pleD fter the 4histogram4 wordD hs to e de(ned wht kind of distriution is desired X suessively x nd y vrilesF xext re de(ned normlisE tion numer @detils in expl4.optnsAD the lowest nd gretest siss vluesD nd the numer of ins wntedF rereD the normlistion vlue 42124 mens tht eh in of the histogrm will e normlised y 1/2πxD its own width nd y the numer of events triggered for this nlysisF he 4idcode 1204 instrution mens tht only prtiles with sh EPOS = 120D i.e. π + D will e onsideredY 4noweak4 indites to ignore ll the prtiles oming from wek deys @ting s perfet feedEdown orretionAF xext ome the triggersD here pplied on the solute vlue of rpidity of the prtiles of interestD nd on the entrlity of the eventF he 4hisfac4 is just normlistion ftorD ounting here for the 1/dy normlistionF pinllyD the 4bimevt4 instrution indites to onsider only events in ertin entrlity lssD whih lower nd higher ounds re spei(ed y the two next vriles 4bim004 nd 4bim054F o summriseD in light of the previous explntionsD this exmple will rete p T distriution @d 2 x π + /2πp T dp T dyA of exlusive π + within |y| < 0.1D for events within entrlity lss HES7 sed on impt prmeter lirtionD distriuted in TH ins etween p T = 0 nd p T = 12 qeF iverything written etween 4beginwrite4 nd 4endwrite4 will then e registered s is in the .histo output (le produedD exept the instrutions within the rketsF hose instrutions indite to write the results of the nlysis s QEolumn rryD nd then the weight ssoited to the urrent histogrmF hile the two (rst olumns lwys ontin x nd y vlues of the insD the ontent of the third olumn nd of the weight depends on if the result of the nlysis is n histogrm @simple distriution for given x vrileA or pro(le histogrm @verged yEvlues for eh xAX for histogrmsD the 4histoweight4 orrespond to the numer of events triggered y the nlysisD nd the third olumn of the results rry ontins the solute sttistis unertinty y/ √ N @N eing the numer of entries in the onsidered inAY for pro(le histogrmsD the 4histoweight4 is set to H nd the third olumn of the results rry ontins the numer of entries in the urrent inF hose di'erenes re due to the ft these di'erent types of histogrms re dded with eh otherD s the nlyses re run eventEyEeventF hey re espeilly importnt for the explntions on the integrtion of ivet in the iy nlysis frmeworkD disussed in the next susetionF sn the endD ll the results otined from the nlyses re stored in one .histo (leD s mentioned in the previous prgrphF sing dedited sript sed on the rsq pkge from the gix tool Physics Analysis Workstation @eA QHTD we n disply the results of ll the distriutions stored in suh (lesD esily omprle with experimentl dt @stored in other dedited .histo (lesA y dding few instrutionsF his relly fst tool whih stores ll the plot under unique ostript (leD whih is onvenient when one wnts to hve quik overview of results for lrge pnels of oservlesD so is relly useful for developersF Centrality denitions in analyses goming k to the nlysis itselfD one ould however wonder why using bEsed enE trlity de(nitions to run n nlysis tht is intended to e ompred with experimentl resultsF sndeedD in experimentsD entrlity is lwys de(ned fter given distriution mesured in given kinemti region @explined in susetion PFPFIAF xeverthelessD UT RFQF sxiqesyx yp si sxy iy exevs pewiyu euse not ll experiments use the sme distriutions to determine entrlity lsses @sometimes done using midErpidity prtiles multipliity IQTD some other times using forwrd nd kwrd prtile multipliity QHUAD we use bEsed entrlity lsses suh tht these de(nition re the sme whtever dt we ompre our results withF sndependently from experimentl resultsD bEsed entrlity de(nition is lso useful when one wnts to ompre the e'et of using hydrodynmis or not in our simultionsD or in other words to ompre pure string model with oreEoron pproh to model rsgsF es mtter of ftD using n hydrodynmil expnsion of the ore will led to produe less prtiles in the pD for the sme initil onditionsD thn with pure string modelF his is due to the ft thtD with )owing mediumD prt of the energy is onsumed y the expnsion of the )uidF hereforeD in order to ensure to ompre the sme events etween themD it is mndtory to use bEsed entrlity lsses for studying suh e'etsF 4.3 Integration of RIVET into EPOS analysis framework sn the urrent setionD s will strt y explining how iy ws upgrded in order to produe event reords under repMC formtD enling thus to perform ivet nlyses on iy eventsF woreoverD motivted y the ft tht ivet provides onstntly growing lirry of nlyses with their orresponding experimentl dtD s will detil then how it hs een integrted to the nlysis frmework of iyF fy 4integrated 4D s do not men tht ivet9s ode hs een merged nd omes nturlly with iy when instlling the ltterF he gol ws to (nd wy to get results from ivet9s nlyses diretly fter runD in the sme .histo (le in whih we get results from iy nlysesD without hving to sve the repMC output (le nd run ivet fterwrdF his wyD results from ivet9s nlyses n e displyed in the sme ostript (le ontining result from ll other nlysesD s explined in susetion RFPFQF 4.3.1 Producing HepMC les he (rst step to mke iy omptile with ivet is of ourse to produe (les under repMC formtD to store the reords of simulted eventsF o do soD s hve tken s sis previous ttempt to produe suh (les y wri tefnik during her hh PUHF xeverthelessD efore explining how s hieved thisD s will rie)y desrie the ontent of the repMC (les in order to present wht informtion hs to e providedD nd how they re struturedF Structure of HepMC event records he repMC (les ontin event reords under text formtD nd re strutured folE lowing linesF ih line strts with ertin hrterD inditing to wht re relted the informtion stored fterF rere is summry of the most importnt onesD with some of their ontent @desriptions re not exhustiveD see QHV for more detilsAX 4E4 lines de(ne the eventsD with informtion on the event numerD the numer of verties reorded in the eventD the rodes of olliding prtilesD etFY 4C4 lines ontin informtion on the rossEsetion of the retion @in piornAY 4H4 lines ontin informtion neessry for rsgs suh s the numer of prtiipnts for projetile nd trget @N targ/proj part AD the numer of proton 8 neutron spettors UU grei RF igrxsgev hiivywix py iy R @N p/n spec AD the numer of nuleonEnuleon ollisions @N coll AD or the impt prmeter bY 4V4 lines ontin informtion on vertiesD suessively their rodeD shD (x, y, z, c.τ ) oordintesD the numer of orphn inoming prtiles nd the numer of outgoing prtilesY 4P4 lines ontin informtion on prtilesD i.e. their rodeD sh PDG D (p x , p y , p z , E) oordintesD mssD sttus @whether the prtile is em prtileD stle p prtile or will deyAD nd the rode of ny vertex whih n hve the onsidered prtile s n inputF en exmple of the ontent of suh (le is shown in (gure RFTD oming from (le produed with iy for peripherl E ollision @b = 13.45 fmA t 2.76 qeGeF he event ontin ISR vertiesD with olliding prtiles hving rodes IHHHI nd IHHHP @s it is ustomryAF prom the originl vertexD loted t (0, 0, 0, 0)D re going out PIVI prtilesD while tking two prtiles inF hose two prtiles re of ourse the prtiles IHHHI nd IHHHPD s indited y the vertex rode EI t the end of their linesD nd y their sttus numerD 4R4D whih orresponds to em prtilesF efter eh vertex re listed ll the prtiles going out from itD with sttus I for prtiles onsidered s stle p prtileF he hdrons or leptons whih lter dey through tndrd wodel proesses re leled with sttus P nd with the rode of their dey vertexD whih re written fterwrdD followed t their turn y the orrespondE ing outgoing prtilesF rereD we n see tht the olliding led nulei @with their tomi nd mss numers expliited in their sh PDG = 1000822080A re followed y p protons nd neutrons with no trnsverse momentum @p x = p y = 0A whih re spettor nuleons from the olliding ionsF E 1 -1 -1.000e+00 -1.000e+00 -1.000e+00 0 -1 154 10001 10002 0 0 U GEV MM C 8.4970962524414062e+10 0.000e+00 H 0 11 16 44 235 154 0 0 0 1.3447725296020508e+01 0 0 0 V -1 0 0 0 0 0 2 2181 0 P 10001 1000822080 0 0 -2.870399e+05 2.8704e+05 1.93729e+02 4 0 0 -1 0 P 10002 1000822080 0 0 2.870399e+05 2.8704e+05 1.93729e+02 4 0 0 -1 0 P 10003 2212 0 0 1.3799996e+03 1.3799999e+03 9.3827e-01 1 0 0 0 0 P 10004 2112 0 0 1.3799996e+03 1.3799999e+03 9.3965e-01 1 0 0 0 0 P 10005 2112 0 0 1.3799996e+03 1.3799999e+03 9.3965e-01 1 0 0 0 0 ... Production of HepMC output les with EPOS sn order to produe the repMC output (lesD s strted from the funtions written previously y wri tefnik in EPOS/src/KWb/ll_hep.cpp @nd its ssoited heder ll_hep.hAD sed on repMC version PFHTFHW QHVF hese (les hd of ourse to e dded in the list of ompiled (les in order to e prt of the iy ompiltionF UV RFQF sxiqesyx yp si sxy iy exevs pewiyu o ll the funtions reting the repMC (le nd writing inD s followed the sme pth in the iy ode s for the prodution of yy (lesF husD s dded the ll of 4open_hepmc()4 nd 4fillhepmc()4 funtions in the 4treestore()4 suroutine nd of 4closehepmc4 funtion in the 4treeclose4 suroutine @oth written in out.fAF hose two suroutines re lled y 4eposevent4 @bas.f AD if the 4fillTree4()4 funtion is lled in the .optns (le @see susetion RFPFPAD when simulting eventsF he sme thing hd to e done in the suroutine 4getCevtCptl4 @in out.fAD whih is lled when reding events reorded in yy (les for reEnlysis @y using the )g 4-cproot4 when lling eposAF purther modi(tions were lso neessry on the ontent of the yy (les t this pointD euse some generl informtion on the events neessry for the repMC (les @N targ/proj part D N p/n spec A were not sved so frF hen reding events stored in those (les for reEnlysisD it ws not possile then to pss the informtion to the repMC reordsD while it ws possile when simulting the eventsF hereforeD s modi(ed the struture of the ree ojets used to store events under yy formt in the (les etree.cppD etree.h nd etreef.cppD dding new rnhes to store those informtionF feuse we don9t wnt the repMC output (le to e systemtilly reted nor sved when reording or reding yy (lesD s they re lled in the sme suroutinesD s reted similr sheme to tivte the reording s for the yy (les produtionF s de(ned new vrile 4ihepmc4 used to indite if the repMC (le hs to e reted nd (lledD nd thus mde the ll of the funtions used to do so @disussed in previous prgrphsA depend on its vlueF henD s hd of ourse to mke the ridge with the .optns (le instrutionsD i.e. llowing the user to ontrol the vlue of this vrile from thereF o do soD s modi(ed the suroutines 4aaset()4 nd 4aread4 @in bas.fAD used to red nd interpret the ontent of .optns (lesD to tivte the repMC (le writing vi the instrutionX set ihepmc 1 sn the sme mnner s for the yy (lesD s lso modi(ed the epos sript to rete 4-hepmc4 )g whih indites to sve the repMC output (le reted one the run is (nishedF pinllyD the most importnt tsk in this work ws to reEwrite the min g++ funtion 4fillhepmc()4D used to rete the event struture nd write it in the output (leF he (rst reson for thtD whih s lredy mentionedD ws to omplete the generl informtion provided out the eventsD ompred to the originl version written y wri tefnikF he seond importnt reson ehind this rewriting ws thtD in the originl verE sionD only the p prtiles of the ollision were reorded in the events stored in repMC (lesF his ws prolemti in the se of feedEdown orretions in nlysesD or studies of exlusive prtile spetr for instneF uh nlyses were not hievle then s no informtion on the prtile9s prents were essileD mking impossile to know if prtiles were produed from hdronistion or from seondry deysF st ould lso e prolemti for the study of shortElived prtiles like qurkoniD s the only wy to hve them reorded in the repMC from iy would then e to use the 4nodecays4 feture in the .optns (lesF st would then hve een impossile to know how suh prtiles dey fterwrdD wht is essentil when ompring to experimentl dt s they re generlly reonstruted through spei( dey hnnelsF roweverD the solution ws not to jump to UW grei RF igrxsgev hiivywix py iy R the other extreme y reording the omplete history of eh event in our repMC output (lesF es it n e seen in the extrt of suh (le shown in the (rst prt of this susetionD peripherl E ollision t vrg usully produes more thn two thousnds prtiles in the (nl stteF eording the entirety of suh events would then tke n inredile mount of disk speD knowing for instne tht the event in question @reorded with only p prtilesA is lredy weighing HFS wfF o overome this prolemD s dded seond possiility for the reording proedure whih sves p prtiles plus their prents @nd potentilly grndEprentsA in ertin sesY the detils on wht is sved extly will e given in the next nd lst prt of the susetionF s even dded third possiility to reord prtiles efore hdroni sdes for eh eventD with the help of exel ve fégueD wster student whom s supervised for his lst yer internshipF his llowed the usge of ivet to look t the impt of hdroni sde on umulnts of prtile netEmultipliitiesD in order to rossEhek the results otined with the iy nlysis frmework whih re presented in hpter SF sn the endD it is possile to swith etween to three versions of the reording proedure y hnging the vlue of the 4which_table4 vrile in ll_hep.cppD eing nevertheless set on the seond version y defultF enother modi(tion hieved on the repMC reording proedure ws to hnge the wy the energy of prtiles is lultedF he kinemti informtion on prtiles provided y iy to the 4fillhepmc()4 funtion re their momentum vetor oordintes nd mssD while in the repMC formt the energy is provided for eh prtile reordedF snitilly using the energyEmomentum reltion E = p 2 + m 2 to lulte their energyD we oserved nonEphysil results of |⃗ p| > E for some prtiles with lrge vlue of momentum in one diretion ompred to the other ones @e.g. very forwrd prtiles with |p z | > 10 3 qe while |p x,y | < 10 -2 AF his issue eing the results of rounding error due to the limited preision of numeril vrilesD we deided to use nother formul to determine the energyD strting from the de(nition of the rpidity y X

y = 1 2 ln E + p z E -p z ←→ e 2y = E + p z E -p z , ←→ e 2y (E -p z ) = E + p z , ←→ p z 1 + e 2y = E e 2y -1 ,
←→ p z e y + e -y = E e y -e -y , ←→ p z = E × tanh(y). @RFQFIA henD using the ft tht

E 2 = m 2 + p 2 = m T 2 + p z 2 with eqution RFQFID one getsX m T 2 = E 2 -p z 2 , = E 2 1 -tanh 2 (y) , = E 2 1 cosh 2 (y)
, ←→ y = rsinh p z m T @RFQFQA whih gives (nllyD when using eqution RFQFQ in eqution RFQFP X

=⇒ E = m T × cosh(y).
E = m T × cosh rsinh p z m T @RFQFRA
sing eqution RFQFR llows (nlly to hieve lultion of energy with the provided informtion from iy without enountering ny lultion issue like the one exposed eforeF he lst mjor modi(tion ws to inlude the possiility to pply rpidity oost to the whole frme of the prtiles from ny eventF his feture is mndtory to proE due repMC (les for symmetri systems like pE ollisions t vrgD s iy lwys simulte ollisions in the enterEofEmss frme while this one is oosted ompred to the lortory frme in these ollisionsF portuntelyD s this oost is purely longitudinlD one n esily lulte the oordintes (p ′

x , p ′ y , p ′ z , E ′ ) in the lortory frme from the ones in the enterEofEmss (p x , p y , p z , E) with the simple vorentz trnsformtionX

    p ′ x p ′ y p ′ z E ′     =     1 0 0 0 0 1 0 0 0 0 cosh(y) -sinh(y) 0 0 -sinh(y) cosh(y)         p x p y p z E     , @RFQFSA
using the ft tht γ = cosh(y) nd tht γβ = sinh(y)D with y eing the rpidity oost eE tween the two frmesF sing this trnsformtionD s just needed to dd in 4fillhepmc()4 the relultion of E nd p z from the enterEofEmss to the l frmeD using the vlue of rpidity oost indited in the .optns (le in suh seD nd stored in the 4rapcms4 vriE leF sn dditionD vrile 4ihepframe4 hs een reted to indite if rpidity oost should e pplied to the prtilesD following the sme philosophy s for the 4ihepmc4 vrileF Content of the EPOS HepMC output o onlude this susetionD here is summry of the physil informtion whih re provided or not in the events reorded in the repMC output (les produed with iyF he (rst importnt point is the rossEsetion informtionD whose vlue provided for pEA nd AEA events is the orresponding pEp rossEsetion vlueF owrds the hevyEion informtion providedD the numer of hrd stterings is not provided s it is not stored in iyD even though the numer of omerons exhnged during the ollision is knownF he numer of spettor protons nd neutrons @N p spec nd N n spec respetivelyA re provided from the rel vlues of the simultionsD to mth with the spetting prtiles reorded t the eginning of the event @inluding the di'rtive sttesAF roweverD the numer of prtiipnts from projetile nd trgets @N proj part nd VI grei RF igrxsgev hiivywix py iy R N targ part respetivelyA s well s the numer of inry ollisions @N coll A re not tken from the tul simultionsD ut from qluer lultions IQVF he reson is tht experiE mentl ollortion use this model to estimte suh oservles when displying results s funtion of themD s lredy explined in susetion PFPFIF fy doing soD we ensure to perform pplesEtoEpples omprison when ompring those vlues provided in iy repMC (les to experimentl dtF sn the defult version of the repMC reordingD mentioned in the previous prtD ll prtiles with lifetime τ > 10 -19 s re reordedD s well s the omplete sequene of following deysD until the p prtilesF o pply this onditionD used minly to give the possiility to hieve feedEdown orretion from wek deys @see gin disussion in previous prtAD s dded list of exeptions for shorterElived prtiles whih hs to e reorded nywyF his feture llows to study the prodution of spei( hdroni speiesD nd ontin for the moment the iy shs of ommonly studied qurkoniX J/ψD ψ(2S)D Ψ(3770) nd the Υ(1/2/3/4S) fmilyF o omplete this listD one would just need to dd the sh EPOS of the prtile@sA of interest to the 4excptn_list4 in the 4fillhepmc()4 funtionF en exmple of prtile dey hin reorded in repMC (le is shown in (gure RFUD where D + meson @prtile n°IHRVUA deys into K + @n°IHRVVA nd ρ + @n°IHRVWAD the ltter deying in turn into π + @n°IIPPPA nd π 0 @n°IIPPQAF rereD K + D π + nd π 0 re onsidered s stle euse they hve een spei(ed s so in the .optns (le with the 4nodecays4 instrutionD s explined in susetion RFPFPF ... P 10487 411 -1.79e+00 3.86e-01 -2.43e+00 3.58e+00 1.86e+00 2 0 0 -11 0 ... V -11 0 -6.12e+11 1.31e+11 -8.29e+11 1.21e+12 0 2 0 P 10488 130 -5.55e-02 -6.01e-02 -1.09e+00 1.20e+00 4.97e-01 1 0 0 0 0 P 10489 213 -1.74e+00 4.46e-01 -1.34e+00 2.37e+00 7.75e-01 2 0 0 -77 0 ... V -77 0 -6.12e+11 1.31e+11 -8.29e+11 1.21e+12 0 2 0 P 11222 211 -1.12e+00 1.64e-01 -4.15e-01 1.21e+00 1.39e-01 1 0 0 0 0 P 11223 111 -6.19e-01 2.82e-01 -9.26e-01 1.15e+00 1.34e-01 1 0 0 0 0 ... Figure 4.7: Example of the record of a decay chain of a particle in a HepMC le for a Pb-Pb collision at 2.76 GeV/A, from the same event displayed in gure 4.6. Note that the precision on numerical values have been truncated for the purpose of the gure.

pinllyD in order to prevent for potentil prolems in the event reordingD s hve de(ned spei( sttus for nonEp prtiles for whih dughter prtiles n not een foundF his sttus ode hs een tken s 12 @s not used in repMC stndrdsAD eE use suh prtiles seem to e p prtile @sttus IA while it is tully not @sttus PAD wht is veri(ed using the iy prtile sttusF o summriseD s hve rought severl improvements to the ontent of the repMC formtted (les produed with iy RD ompred to the (rst version inluded y wri tefnik PUHF he (rst mjor hnge ws to dd more )exiility in its useF yne n now llow to tke into ount rpidity shifts of the enterEofEmss of the system in se of symmetri ollisionsD or y letting the hoie of reording either only p prtilesD or lso their prents to enle wek deys reonstrutionF woreoverD the user n now VP RFQF sxiqesyx yp si sxy iy exevs pewiyu tivte repMC (les prodution ut without hving to reord it in the endD in order to enle the use of ivet without sving (les uselesslyF enother importnt hnge ws to dd more informtion to the reordsD y pssing more input vrilesD like the numer of prtiipnts or spettors from eh ollisions for instneF pinllyD s hve modi(ed the wy kinemti vriles stored in repMC re lulted from the informtion provided y iyD y using more roust formule to void numeril errors in the lultionsF 4.3.2 Automating the usage of Rivet he prodution of repMC output (les with iy llows now to perform ivet nlyses on the results of its simultionsF roweverD s explined in the introdution of this setionD we hve deided to go further with iy y using ivet s dt nd nlysis lirryF o this endD s inluded the possiility to ll it vi the iy nlysis systemD nd to store the results in our own output .histo (lesF ell the sripts s hve reted for the purposes desried in this setion n e found in the iy repository in EPOS/Misc3/Rivet/F Adapting the experimental data format sn order to use ivet s dt lirry for the iy nlysis frmeworkD it ws neE essry to dpt the formt of the dt provided vi ODA (les in siF es mtter of ftD iy hs its own nlysis lnguge @presented in susetion RFPFQAD nd dt hs to e stored in spei( wy to e lled with itD using the sme struture s for the results of nlysesF en exmple of the ontent of suh (le one trnsried will e shown furtherF o hieve this tskD s deided to write everything in ythonD whih is relly onE venient tool for suh opertionD dded to the ft tht it ene(ts from very good doumenttion on the internetF reneD s reted fully utomted progrm lled RIVET_to_histo.py emedded with user interfeD to o'er severl possiilities of useF efter sking for tehnil informtion @the pth to ivet nd the ddress of diretory where to store the reted (lesAD the progrm sks the user for Q di'erent wys to proessF hey n hoose whether they wnt to onvert ll experimentl dt proE vided with ivetD only seletion of them whih nmes mth list of entered keywords @4seletion mode4AD or ll of them exepted some whih nmes mth list of entered keywords @4exeption mode4AF pinllyD the user n deide if ll of these dt hs to e written in one (leD whih they n nmeD or to write in severl (les depending on the di'erent experimentsD with limit on the size of eh (le writtenF he resulting .histo (les will ontinD for eh di'erent pulition orresponding to set of dtD heder with informtion on the pulition @tken from the ssoited .info (le in ivetAF ih dt tle is then stored with plot hederD giving informtion on its ontentD i.e. title nd xes lels @tken from the ssoited .plot (le in ivetAF sf no informtion re provided in the .plot (leD whih is the se for some nlyses suE mitted to ivetD the plot heders re simply left emptyF pinllyD the nme given to eh dt tle is simply omposed of the nme of the nlysis it elongs toD with series of Q numers sed on the ODA numeringX 4d..-x..-y..4F en exmple of the ontent from .histo (le is provided in the next pgeD sed on e pulition for whih s hve written myself the ivet nlysisF he results otined with iy with this nlysis will e shownD mong otherD in hpter SF fy writing the forementioned progrmD s relised tht it would e useful to struture it in modulr wyD so tht prt of the ode with spei( purpose ould e used in other VQ grei RF igrxsgev hiivywix py iy R ontextsF he ODA formt eing now stndrd formt proposed to downlod dt from HephtD the prt responsile for reding ODA (les nd storing their ontent @dt tlesA ould e useful for other tsksF ith this in mindD s wrote kind of library (le lled EPOS_DATA_lib.pyD in whih s wrote di'erent funtions suh s the one evoked in the lst sentene to store dt from ODA (leD 4Read_yoda_file()4F ith the sme logiD s lso wrote funtion lled 4Write_histo()4 whih writes .histo (les from provided dt tlesD in the sme formt s the exmple displyed in pigF RFVF hese two funtions hs notly een useful when s hd to write nlyses using the iy dedited systemD to ompre iy simultions with experimentl dt for whih no nlyses were ville in ivetF en exmple of how to use 4Read_yoda_file()4 nd 4Write_histo()4 to onvert dt tles from ODA to .histo formt is ville in EPOS/Misc3/Rivet/Simple_templates.pyD with orresponding explntory notesF -------------------------------------------------------------- ------------------------------------------------------------- Using Rivet from the EPOS analysis system rving stored the experimentl dt to ompre our simultion results with in the right formtD s hd to (nd wy to mke the link etween iy nd ivetF es the repMC (les need to e (lled efore running ny ivet nlysis on itD the (rst step ws to dd new kind of output (leD ontining the informtion on whih nlysis to perform one iy run endsF hese new output (lesD with .dataR extensionD re reted when the 4rivet4 instrution is written in the .optns (leD followed with VR RFQF sxiqesyx yp si sxy iy exevs pewiyu the nme of the nlysis to perform nd y whih plots to sve in the .histo (leF es n exmpleD the following instrution will rete .dataR (le with the informtion 4ALICE_2010_S8625980 d03:log/d064 insideX rivet ALICE_2010_S8625980 d03:log/d06 he (rst instrution refers to the required ivet nlysisD nd then the plot numers whih n e provided only prtillyD so tht ll the plots mthing the prtil numering will e sved in the .histo (le in the endF st is lso possile to speify wht sle to use for the y xis when displying the plotD s this informtion is not lwys provided in ivet nd the defult liner sle is not lwys ppropriteF st of ourse possile to ll severl ivet nlysesD y writing one line for eh nlysis in the .optns (leF sn order to exeute ivetD s wrote ython sriptD rivet_analysisD whih is lled in the epos sript one iy hs runF st tkes the .dataR (le s n inputD reds nd store the informtion written insideF henD it runs eh nlysisD reports ny error messge potentilly enountered during the runD nd lls nother progrm to sve the results from plots seleted y the user into the .histo (le @y defultD ll plots re svedAF his progrmD RIVET_to_histo_analysis.pyD is lled one per nlysis nd is lso written in modulr wyD sed on funtions de(ned in EPOS_DATA_lib.pyF he (rst oneD 4Read_yoda_analysis()4D will red nd store the results of the nlysis from the plots seleted y the userD s its nme inditesF st will then get the plotting informtion from the ivet .plot (le using the 4Read_plot_file()4 funtionD nd (E nlly write ll the results of the plots stored in the .histo (leF st will write s well the instrution to ll the orresponding experimentl dt stored to ompre withD from the .histo (les reted s desried in the previous prtF sn the endD the intermediry ODA (le is deletedD s well s the HepMC (le if the 4-hepmc4 )g hs not een used when exeuting eposF es the ODA (les resulting from nlyses do not provide diretly the yEvlues for eh inD ut the omplete informtion on its (lling @sum of weightsD numer of enE triesD etFAD the funtion 4Read_yoda_analysis()4 hs to lulte these yEvluesF his lultion will vry depending on the nture of the distriutionD whether it is lssiE l histogrm or pro(le histogrmF es explined in susetion RFPFQD the vlue of the 4histoweight4 nd the ontent of the third olumn will depend on the type of histogrmF his is of importnt when dding the results of di'erent runs for the sme histogrmD i.e. when merging di'erent .histo (lesF o ensure the informtion re provided orretly for the di'erent types of histogrmD s onduted test X running twie n nlysis on two di'erent set of eventsD otining thus two (les Test1a.yoda nd Test1b.yoda whih s sved nd merged using ivetD nd then trnsried into Test1.histoY repeting the sme opertionD ut trnsriing the results of the plots diretly into .histo (les Test2a.histo nd Test2b.histoD nd merge them into Test2.histo using dedited sript reted y my supervisorF gompring the results of Test1.histo nd Test2.histo show then lmost no di'erenesD or only tiny ones of the order of the sixth deiml digit due to numeril preisionD proving tht the informtion were orretly providedF VS grei RF igrxsgev hiivywix py iy R 4.3.3 Dealing with centrality calibration he use of hevyEion nlysesD nd lso some nlyses regrding highEmultipliity pEp eventsD requires to run lirtion nlyses in ivet s presented in susetion RFIFIF xeverthelessD exeuting suh nlysis for eh iy run to use the results for the nlyE ses of the sme run is not proper solutionF ih run ontin only frtion @generlly smllA of the totl numer of events simulted for the orresponding systemD so the liE rtion distriutions re not representtive of the whole ensemleD nd would even vry from run to notherF sn the endD eh run would give results sed on di'erent liE rtionD ompletely distorting the results of the onerned nlysesF o void this prolemD we proeed like for the mngement of entrlity lirE tion in the iy nlysis frmework @see susetion RFPFQAF e strt y retingD for eh systemD (le lled icl[...]_rvt.optns ontining de(nitions of entrlity lsses sed on impt prmeter nd multipliityD stored in EPOS/KWt/ with the regulr icl[...].optns (lesF e lso store in this sme diretory the originl ODA (le from the orresponding ivet lirtion nlysis used to get these de(nitionsF henD we run simultions where we ll the ivet lirtion nlysesD using spei( instrution in the .optns (le whih is slightly modi(ed ompred to the one used for regulr nlysis X rivet calib_run STAR_BES_CALIB[mult/imp] his will sve the resulting ODA (leD relulte the di'erent entrlity lsses sed on the new distriution nd ompre them to the one stored in the icl[...]_rvt.optns (lesF his lultion is done either with the multipliity or impt prmeter distriuE tionD depending on the prmeter spei(ed etween rkets @4mult4 eing the defult se if nothing is inditedAF es for the nlyses requiring entrlity lirtion s n inputD we provide the distriution from the ODA (le otined with prior simultionD stored in EPOS/KWt/F sf the entrlity de(nitions of the new simultions di'er too muh from the ones stored in icl[...]_rvt.optnsD we hnge the ltter ones y the new onesD nd reple the old ODA referene (le in EPOS/KWt/ y the newly otined oneF sn suh situtionD we need to run gin the nlysis on the sme set of eventsD to ene(t this time of n updted de(nition of entrlity lsses orresponding to these eventsF his rossEhek nd updte of entrlity lirtion distriution is however only neessry for developers when operting hnges in the prmeters from one iy version to notherF he users willD of ourseD not hve to perform suh proedureD s the icl[...]_rvt.optns provided with the inoming puli version will e sed on events otined with this sme versionF xote (nlly thtD s there re sometimes di'erent entrlity lirtion nlyses for one kind of ollisionD euse eh experiment hs its own wy to perform itD we reord the informtion for eh di'erent nlysisF 4.4 Summary of the technical work s hve explined in this hpter how s dded the possiility to rete new output (le with iyD to reord the events simulted in the repMC stndrd formtD mking it omptile with ivetF sn order to go even furtherD s hve then developed ode rE hiteture to hndle the use of ivet vi the iy nlysis systemD tking into ount VT RFRF wwe yp ri igrxsgev yu the neessity of entrlity lirtionsF o sum it upD s will rell the di'erent steps to follow in order to use these new feturesF o mke the most omplete desription possileD s will use s n exmple the ll of n nlysis from the eve ollortion dedited to the study of η density distriution of hrged prtiles for pE ollisions t SFHP eGeF he (rst step is of ourse to on(gure pPb5T.optnsD in order to produe the HepMC output (le nd to tke into ount the rpidity shift of the enterEofEmss ompred to the l frmeF henD one hs of ourse to ll the desired nlysisD here 4ATLAS_2015_I13864754F he ssoited lirtion nlysis is lled tooD to enE sure tht the preEreorded distriutionD stored in EPOS/KWt/iclpPb5T_rvt.optns henD one simply hs to run iy @here with the )g to sve the produed repwg (le with the events reordedD not mndtory thoughAX $> epos -hepmc pPb5T

!################################################################ ! STAR Data: !"Bulk
/A) !################################################################ !-
xote tht the pth to ivet is expeted to e de(ned s n environment vrileD nd so does not need to e written nywhereF sn order to lrify the funtioning of the mhinery introdued in detil in the previous setionD nd triggered when using suh instrutionsD n illustrtion is given in the (gure RFIHF hereD the (les in lkGwhite re permnent (lesD exept for pPb5T.hepmc whih n e sved or not following user9s willD nd (les in grey re temporry (lesF tright lines represent proesses hieved y iyD while dshed lines show proesses hieved y rivet_analysis pinllyD the dotted lines ount for the proesses whih re hieved y RIVET_to_histo_analysis.pyF iven though the use of ivet through the iy nlysis system is now fully funE tionlD some potentil improvements n still e mdeF yn ivet9s sideD the min limit for the developers is of ourse the lk of nlyses for rsgsD whih s lredy mentionedF e nnot rely exlusively on it to perform our omprison with experimentl dt yetX we need thus more ontriutions from the experimentl ollortions to mke of ivet the perfet tool it hs the potentil to eD in the exhnges etween theoretil nd exE perimentl ommunitiesF yn iy9 sideD one minor tehnil issue still remins in the VU grei RF igrxsgev hiivywix py iy R reording of e + Ee -ollisions @or for other leptoni systemA with repMCD s the inforE mtion on olliding prtiles re not reorded orretlyF feyond thisD the use of ivet ould e improvedD y llowing the user to sve the ODA (le produed so tht they n disply the results diretly using the 4rivet-mkhtml4 ommndF enother improvement would e to enle to perform the ll of ivet9s nlyses with pirstEsnD pirstEyut @pspyA pipeD so tht events stored y iy under repMC formt would e red in ontinuous )ow s soon s they re reordedF vetting the user getting rid of the repMC (les one the nlyses re performedD if they do not need itD llows to sve memory spe over runsD nevertheless it still tkes spe for the time of the runD whih ould e limiting when reding lrge numer of events in one runF he setion SFI will e entered on si oservles tht re η distriutions of hrged hdrons nd p T spetr of identi(ed prtilesF here re two golsX (rst of ll ensuring tht prtile prodution is well reprodued y iy in the kinemti rnge of interest for the study of umulntsD nd lso using this osion to disply (rst physil results from iy RF husD s will espeilly onentrte on the entrl @|η| < 0.5A nd lowEp T @p T < 2 qeA region of the phse speD where the prtiles used in the umulnts nlyses re oming fromF st will lso e the osion to hek until when n iy o'er good desription of the physis of rsgsD while going down in energyF pollowing the simple resoning exposed in susetion QFQFQD the fq used to desrie the initil intertions is not expeted to e relevnt nymore elow ∼ 20 qeGe in rsgsD wht the results displyed here will enle to verifyF sn setion SFPD s will expose ll the results otined for the study of 2 nd order umuE lnts of netEhrges nd their proxiesF vet me rell rie)y the min ojetivesD motivted y the pulitions presented in susetion PFQFQ nd exposed in setion QFSX E to ompre the proxies used y e in PIID nd the enhned proxies proposed in PQRD to the umulnts of ssoited onserved hrges BD Q nd S Y E to quntify the impt of the hdroni sdes on those oservles Y E to estimte the proportion of the signl originting from the oreD the prt mimE iking the )uid ehviour of q in iy simultionsF ell the results from iy used from now on in this hpter re otined from simuE ltions run with one of the lst nd most dvned iy R et versionsD iy QFRSID unless spei(ed otherwiseF hey hve ll een performed with the oreEoron proedure tivtedD nd the susequent reltivisti )uid dynmil evolution of the ore using the Qp eqution of stteF woreoverD hdronistion of the ore is hieved vi the miroE nonil proedureD whih ensures oth lol nd glol onservtion of the onserved hrgesD desried with the other fetures in setion QFRF feuse the version used is quite reentD nd the simultion of suh ollisions is very demnding in terms of omputE ing resoures @even when using dedited omputing entre 1 AD the sttistis ville for eh ollision energy is very limitedF es shown in tle SFID results from iy re sed on ∼ 250k events per energyD ompred to the severl millions generlly used in experimentl nlyses IUUF he generi results presented in this setion will e divided into two prtsD one for eh of the two reviewed oservlesD whih hve een oth introdued in susetion PFPFIF husD the (rst susetion will del with the sptil distriution of produed hrged hdronsD vi the mesurement of pseudorpidity @ηA prtile densityF he seond prt will then over the trnsverse momentum distriutions of identi(ed prtilesD strting with the lightest ones @π ± D K ± nd p/pA to then expose the strnge hevier ones @ΛD ΛD Ξ -D Ξ + D Ω -nd Ω + AF his wyD s will hek tht the prodution of ll the prtiles used lter in the study of umulnts is reltively well reprodued y the set of simulted events usedF feuse experimentl dt re not ville t ll energies for every oservles in euEeu ollisionsD or simply euse of redility when it9s the seD s will not show results for the eight di'erent energies for eh oservleF hen the hoie is possile mong ll ollision energies @or lmostA thoughD s will try to hve the widest nd most regulr energy sn possileF gonerning the ollision entrlityD ll results displyed in this setion hve een otined y using the impt prmeter distriution to determine the entrlity lssesD for the resons explined in the end of susetion RFPFQF ell the nlyses whose results re shown in this hpter hve een written y myselfD nd performed using the iy 4onEtheErun4 nlysis frmeworkD desried in susetion RFPFQF hey represent n importnt mount of workD s eh of them require to underE stnd properly how the nlysis hs een hieved on the experimentl sideD espeilly regrding the orretion of feedEdown from wek deysF he resonD lredy mentionedD for still using this system is tht only few nlyses for rsgs re ville so fr in ivetD nd very smll numer for the energy rnge of the fi progrm espeillyF he only exeptions re the p T spetr of light hdrons for √ s N N ≤ 39 qeD otined from ivet nlysis 2 @minly written nd sumitted y myselfA y using the new frmework desried in setion RFQF

√ s N N @

Pseudorapidity densities of charged hadrons

sn order to ensure tht the sptil distriution of hrged prtiles is orretly reE produed y iyD we study their pseudorpidity densitiesD i.e. the numer of hrged prtiles per pseudorpidity unit dN ch /dη s funtion of ηF sn (gure SFI re shown the results from iy QFRSI ompred with dt from the ryfy experiment for euEeu ollisions t IWFTD TPFR nd PHH qeGe QHWF he experimentl results hve een otined using the ryfy detetor overing lmost the whole zimuths in the region -5.4 < η < 5.4D with entrlity determined thnks to the energy deposited in detetors overing 3 < |η| < 4.5D independents from the ones used for the mesureF he hrged prtile distriution re orreted from ll kinds of kground ontmintionD nd spei(lly from the feedEdown of hrged prE tiles originting from wek deys @like K 0 s D ΛD Ξ nd Ω deysA QHWF reneD s lso orreted for feedEdown of wek deys in the nlyses of the simulted eventsF wonte grlo simultions hve lso een used to orret the distriutions for missing hdrons whih re not deteted t very low p T Y the dt re thus onsidering the whole p T rnge @0 → ∞ qeAF yne oserves for ll energies typil struture with two umps t forwrd nd kwrd rpidity regionsD whih re used y oron prtiles oming from the frgE menttion of exited remnnts fter the initil intertions PWHF sn the entrl regionD the vst mjority of prtiles re oming from the oreD or the 4entrl plteu4 in the piture depited y fjörken @introdued in susetion PFIFIAF reneD the umps re more seprted when em energy inresesD euse the rpidity of olliding nulei @nd so the one of their remnntsA inresesF sn the entrl region |η| < 0.5 whih is of most interest for us euse of the study presented in setion SFPD iy simultions re in greement with experimentl dt for ll results presentedD even though generlly on the lower side within the error rsF he only exeption is for very entrl @HEQ7A ollisions t IWFT qeGeD where the remnnts ply n importnt role s they re loser to eh otherD nd seem to overprodue hrged prtiles nd thus ontminte the entrl η regionF xote nevertheless thtD ompred to iy QFRRRD n erlier et versions of WP SFIF fesg ige py ri fi ixiqsi iy R PVQD the simultions re in etter greement with dt t PHH qeGe thnks to n improvement of the tretment of remnnts frgmenttionF 5.1.2 Transverse momentum spectra of identied hadrons he p T spetr displyed in this susetionD omined with the previous pseudorE pidity densitiesD re essentils to legitimte the events simulted with iy QFRSID t lest for prtile prodution in the kinemti rnge onsidered in setion SFPF hue to the ft tht the runs of euEeu ollisions t di'erent energies t rsg hs not een ll performed in short timeD there is no single systemti nlysis of p T spetr for ll hdroni speies t ll energiesF snstedD the severl sets of dt used here re oming from di'erent experimentsD nd thus with di'erent kinemti rngesF sn order to hve n similr view ross the di'erent energies nd identi(ed hdrons hekedD s will only disply results in the rnge 0 ≤ p T ≤ 2 qeD even when experimentl results re ville for lrger p T rngeF Light hadrons vet (rst strt with the light hdrons @i.e. π ± D K ± nd p/pAD for whih simultions will e ompred to experimentl dt for √ s N N = 7.7D IRFSD PUD TPFR nd PHH qeD lthough results re ville t ll energies simultedF he reson for hving hosen these prtiulr energies is tht eh of these steps orresponds pproximtely to the doule of the energy of the previous oneD nd spns hene the whole rnge of the fi energiesF trting from the highest energyD the (rst results to whih s9ve ompred iy simE ultions with dt oming from the rixs experiment QIHF he p T spetr hve een otined using the midErpidity rnge of |η| < 0.35D nd orreted to ount for the inomplete zimuthl overge of the detetor with the help of simultionsF he events nlysed hve een divided into (ve entrlity lssesX HEIH7D IHEPH7D PHERH7D RHETH7 nd THEWP7F he feedEdown from wek deys hve een orreted with wonte grlo methods for ll light hdron speiesF he resultsD plotted in (gure SFPD show pretty good greement etween iy QFRSI nd experimentl dtD exept for slight overestimtion in peripherl eventsF por euEeu ollisions t TPFR qeGeD the only ville dt of identi(ed hdrons p T spetr re oming from the ryfy ollortion QIIF feuse this nlysis ws hieved using the spetrometer rms whih over restrined phse speD the mesurement hve een mde for y = 0.8 only nd with limited zimuthl overgeD whih hs een extrpolted then to ount for the 1/2π normlistionF he events used hve een divided into three entrlity lsses orresponding to HEIS7D ISEQH7 nd QHESH7 of the totl rossEsetionF peedEdown orretions hve only een pplied to @ntiAprotons distriutionD y seleting only the ones with distne of losest pproh @hgeA < 0.35m from the intertion vertexF uh method rejets nturlly ll the seE ondry protons originting from the wek deys of strnge ryons like Λ @cτ = 7.89mA or Σ + @c.τ = 2.40mAF roweverD it ws estimted to rejet only ∼ 25% of the totl feedE down protonsD thus the orretion ws minly hieved thnks to estimtions otined y simultionsF he π ± nd K ± spetrD in turnD hve not een orreted from ny feedEdownF he omprison etween iy QFRSI simultions nd experimentl dt for this energyD displyed in (gure SFQD show gin n exellent greementF he only deviE tion oserved for the proton spetr might ome from smll protons overprodution from iyD ut the feedEdown orretion method pplied y ryfy should not e WQ grei SF fiew ixiq gex 8 h yp gwvex sr iy negleted neither to explin this di'ereneD s it only onsidered two possile soures of feedEdownF he most detiled nlyses of light identi(ed hdrons p T spetr hs een delivered y the e ollortionD in IUU for euEeu ollisions t UFUD IIFSD IWFTD PU nd QW qeGeD nd in QIP for the ones t IRFS qeGeF hey used prtiles deteted within |y| < 0.1 in full 2π zimuthl overgeD nd divided events into nine entrlity lssesD i.e. HES7D SEIH7 nd IH7Elrge lsses from IH to VH7F he feedEdown orretion onsists of hge< 3m seletionD whih works e'etively well for π ± ut not for p/pD onsidered then s not orretedF esults for K ± eing lmost not 'eted whether this seletion is pplied or notD s deided nevertheless to orret them from the feedE down ontmintionF feuse of the numerous entrlity lsses used in this nlysisD s hve splitted the spetr for eh light hdron into P plots for redility Y thereforeD results for √ s N N = 7.7D IRFS nd PU qe re to e found in ppendix eF eginD results

WR

SFIF fesg ige py ri fi ixiqsi from iy QFRSI re in very good quntittive greement with experimentl dt for PU qeGeD displyed in (gures eFI nd eFPD whtever speie onsideredF et IRFS qeGeD for whih results n e seen in (gures eFQ nd eFRD π ± nd K ± spetr re lso very well reproduedD ut the ones for p nd p re found to get slightly steeper slopes thn dtF pinllyD the sme oservtion n e mde t UFU qeGeD ut this time for ll speies nd even more entutedD s shown in (gures eFS nd eFTF hereD the sudden drop of some iy urves re simply due to lk of oserved prtiles in the onsidered insD euse of the reltively smll numer of simulted events used in the nlysesF Strange baryons s will know expose the di'erent results of iy QFRSI for the prodution of the hyE perons ΛD Ξ -D Ω -nd their respetive ntiprtilesD still for the rnge 0 ≤ p T ≤ 2 qeF es there re no experimentl results t IRFS nd TPFR qeGe omprle to the ones WS grei SF fiew ixiq gex 8 h yp gwvex sr iy from lst setionD s will review in this se euEeu ollisions for √ s N N = 7.7D PU nd PHH qeD proeeding in the sme wy y going down in energyF he results t PHH qeGe re oming from e pulition using (ve di'erent entrlity lssesX HES7D IHEPH7D PHERH7D RHETH7 nd THEVH7 QIQF he Λ nd Λ hve een mesured within |y| < 1D reonstruted vi the spei( topology of their wek deE ys Λ → p π -G Λ → p π + y seleting @ntiAprotons with hge> 0.9m nd pions with hge> 2.85m QIRF woreoverD they hve een orreted from the feedEdown of Ξ nd Ω hyperonsD wht hs onsequently een done in iy results s wellD with strit feedEdown orretion from ll wek deysF he ltter ones re mesured within |y| < 0.75D reonstruted vi the proesses Ξ → Λ π nd Ω → Λ K respetivelyD nd did not require ny spei( feedEdown orretionF sn order to inrese the sttistisD oth Ω -nd Ω + re omined in the sme distriutionsF WT SFIF fesg ige py ri fi ixiqsi he seond pulition on whih my study of hyperons prodution is sed is lso from the e ollortionD tretingD like in the se of light hdronsD ollisions for UFUD IIFSD IWFTD PU nd QW qeGe QISF he spetr hve een distriutedD for Λ nd Ξ ryonsD into the entrlity lsses HES7D SEIH7D IHEPH7D PHEQH7D QHERH7D RHETH7 nd THEVH7 for ll energiesD while this reprtition vries with energy for Ω ryons due to sttistisF eginD Λ nd Λ re orreted from the feedEdown of hevier hyperons Y they re nevertheless ontminted y the eletromgneti feedEdown of Σ 0 D s they n not e distinguished due to their very short lifetime @∼ 10 -19 sAF por iy resultsD the sme proedure hve een ppliedD with strit feedEdown orretion on wek deys ut no orretions from Σ 0 deysF gontrry to the reonstrution method used for the results t PHH qeGeD ll strnge ryons disussed here re mesured within |y| < 0.5F qeF his systemti study tends thus to on(rm tht iy is not relly suited to simulte rsgs t low energies @i.e. elow PH qeGeAD s expetedF st strtsD from these energiesD to show signi(nt di'erenes with dtD even though not ompletely o' the mrkF sn prtiulrD the softening of the p T spetr ompred to the experimentl results t low energies might result from the instntneousness ssumption of the primry WV SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi intertionsD equivlent to ssume very thin olliding nuleiD limittion disussed lredy in susetion QFQFQF roweverD euse of smller vorentz oostD the nulei hs thiker longitudinl extension t low energiesF reneD the prtiles produed erly t midE rpidity might lose more energy s they ould e slowed down y the olliding nuleiF his would result into shift of prtiles towrds lower p T vluesD s iy simultions showF wenwhileD in more relisti piture tking into ount the (nite extension of olliding nuleiD the prtiles ould e produed lter s the nulei get through eh otherF hose prtiles would thus lose less energy y esping the intertion regionD s they would fe less of the remining nulei mtter on their wyF hisD on the ontrryD would result into less steep slope of the p T spetrD s oserved experimentllyF 5.2 Study of the 2 nd order cumulants of conserved charges he results from the previous setion reveled tht iy QFRSI seems essentilly le to reprodue properly the prodution of light hdrons nd hyperons down to ∼ 20 qeGeD s expetedD in the kinemti rnge 0 < p T < 2 qe t midErpidityF felow this energyD the results from simultion show inresing devitions regrding experimentl dt s energy deresesD ut sty reltively lose to it down to UFU qeGe stillF reneD iy QFRSI ppers to e dequte for the study of 2 nd order umulnts whih hs een motivted in susetion PFQFQD nd should e le to reprodue the vrines nd ovrines mesured y e in PIIF hereforeD s will strt y showing in the (rst susetion the results from iy simuE ltions for the @oAvrines of netEπD netEK nd netEpD s well s the relted rtios C Qp D C QK nd C pK de(ned y the formule @PFQFIVAF he ojetive isD in ftD to ompre them with the results from eD in order to hek if those results re orretly reproE duedF henD in susetion SFPFPD s will disply the omprison etween these proxies nd the enhned ones suggested in PQR lulted from iy simulted eventsD nd the ext 2 nd order umulnts rtios of BD Q nd SF sn this wy s n verifyD with dynmil simultions of rsgsD if the proposed enhned proxy rtios enle to etter reprodue the results from ext onserved hrgesF pinllyD in susetion SFPFQD s will expose the results of the estimtion of the impt of the lte stges of the ollision on those oservE lesD mde possile y the modulr oneption of iyF s will show s well how muh of the signl efore hdroni sdes is originting from the oreD whih plys the role of q in iy simultions nd is thus the prt whih goes through phse trnsiE tionF sndeedD if there were to e )ututions emerging from the presene of ritility in the evolution of the systemD it would e rried y the prtiles produed from the oreF sn this setionD s will exlusively fous on the results nd their physil interprettionF husD ll the detils out the nlysis employed to get those results from iy simE ultions re given in the ppendix gF hereD the nlysis routine is detiledD nd some informtion out its tehnil implementtion re lso providedD s well s n exmple of how to run it vi the iy nlysis frmeworkF hile results t ll energies will e used for plots s funtion of √ s N N D results s funtion of the entrlity @displyed y N part A will e provided only for UFUD IRFSD PUD TPFR nd PHH qeGe for redilityF 5.2.1 Results for STAR proxies: variances, covariances and their ratios he (rst stepD si ut very importntD is to verify if iy n reprodue pproxE imtely well the experimentl distriutions of @oAvrines of netEπD netEK nd netEp nd relted rtios from PIIF es reminderD ll those prtiles re mesured within WW grei SF fiew ixiq gex 8 h yp gwvex sr iy |η| < 0.5D hve 0.4 < p T < 1.6 qe nd hge< 1m from the intertion vertex in the experimentD so the sme uts hve een pplied in the nlysis of simulted eventsF xote thtD from these @oAvrinesD the rtios C Qp nd C QK from eqution @PFQFIVA re otined vi the reltions @for oth e nd iy resultsAX

C Qp = σ 11 Qp σ 2 p = σ 11 πp + σ 11 pK + σ 2 p σ 2 p = σ 11 πp σ 2 p + σ 11 pK σ 2 p + 1 @SFPFIA C QK = σ 11 QK σ 2 K = σ 11 πK + σ 11 pK + σ 2 K σ 2 K = σ 11 πK σ 2 K + σ 11 pK σ 2 K + 1 @SFPFPA
s hve deided to lulte the displyed umulnts s funtion of N part diretlyD insted of pplying the gfg introdued in susetion PFQFPF he (rst reson is tht iy enles this fetureD s one n ess this quntity on n eventEyEevent sis in the simultionsF sn order to relly ompre pples to pplesD s used the qluer estiE mted N part vluesD nd not the one provided y the fqD s e uses the qluer model for entrlity determintionF eondlyD it llows to hve lerer resultsD nd re simpler to lulte s they do not require intermediry lultionF woreoverD study of the impt of the size of entrlity lsses lredy shown tht for 2 nd order umulntsD there re no e'ets visile whether orreting or not from the gfi PPRF sn order to ensure itD grdute student s hve supervised for n internship hs performed the nlysis using oth N part diretlyD nd the gfg for the sme entrlity lsses s the ones used y eF re hs notly used ivet to ode the nlysisD tking dvntge of the new possiility o'ered y the system s hve elorted nd presented previously in hpter RF sing RH ins in N part D he found solutely no di'erene etween the diret method nd the gfg methodD the points otined with the ltter one mthing perE fetly with the urved otined with the former oneF hose results re shown for euCeu t √ s N N = 200 qe in (gures fFI nd fFPF fesides on(rming the results from PPRD it ws lso expeted s using RH ins is roughly equivlent to onsidering PFS7 entrlity lssesD wht lrgely redues volume )ututions ompred to the IH7 entrlity lsses of eF he results for the vrines re displyed in (gure SFUD ompred with the dt from e presented in PFQFQF eove ∼ 20 qeGeD iy results re qulittively good s IHH SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi they show liner inrese with deresing entrlity of the ollision @↔ inresing of N part A s expetedF till in this energy rngeD the results re glolly good on quntiE ttive levelD exept for the netEπ vrine t TPFR nd PHH qeGe whih re very slightly overestimtedF uh devitions from dt re usully used y either glol overproE dution of oth π + nd π -D for this preise seD or n imlne in their prodution with more π + thn π -produedD ompred to dtF sndeedD looking t eqution @PFQFIRA s repet hereX

σ 2 α = ⟨δN α 2 ⟩ -⟨δN α ⟩ 2 ,
one understnds tht modi(tion of δN α y ftor c α D used y ny of the previE ously mentioned resonsD would ount for hnge of σ 2 α y ftor c 2 α F hysilly spekingD it n e understood y the ft tht when the glol multipliity of sysE tem is higherD there re more di'erent on(gurtions @or miroEsttesA possile nd then the vrine of the distriution inreses s )ututions re more importnt from one event to notherF husD lthough the prodution of hrged pions seemed to e perfetly reprodued y iy in the results exposed in the previous setion for TPFR nd PHH qeGeD vrines re pretty sensitive to multipliity vritionF woreoverD the results in question for p T spetr of hrged pions t those two energies re ompred to dt from di'erent experiments thn eD i.e. ryfy nd rixsD wht ould lso ply roleF felow ∼ 20 qeGe howeverD the results from iy devite from liner inreseD even further s the energy deresesF his is no surprise onsidering the onlusion from lst setionD whih showed tht in this rngeD iy do not reprodue very well prtile produtionF sn prtiulrD the huge overshooting of σ 2 p for entrl ollisions t UFU qeGe n e diretly onneted to the results in (gure eFTD where proton prodution exeeds dt for the whole displyed p T rnge while ntiproton prodution is glolly underesE timtedF hespite this filure t low energyD the slope vrition of the vrines for the whole srutinised energy rnge is nonetheless well reproduedD even though not lwys in the right proportionF he results for the ovrines re shown in (gure SFVF rereD sttistil )ututions re fr more importnt euse of the reltively smll numer of events nlysed for eh energy @see tle SFIAF tillD the tendenies show y results otined with iy mnge to reprodue well the experimentl mesurements on vergeF he only ler IHI grei SF fiew ixiq gex 8 h yp gwvex sr iy disrepny with dt is seen for σ 11 pK t UFU qeGeD ut iy is still le to reprodue the prtiulr hnge of sign of this oservle round PH qeGeD s mesured y eF his is ll the more notle s rwh loneD whose results re shown in omprison with the dt in the e pulition PIID otins signl omptile with zero t high energy for this ovrineF pinllyD the otined rtios C pK D C Qp nd C QK re presented in (gure SFWF hi'erenes etween iy results nd e dt re oviously visile t UFU qeGeD due to the devitions of @oAvrines disussed preedinglyF xeverthelessD the greement is good mong the other energies for ll three rtios within sttistil )ututionsF e slight entrlity dependene is potentilly visile for C Qp nd C QK t the two top energies thoughD while e dt re entrlity independentF es (rst onlusionD the results of this susetion tend to indite tht iy is pproprite to led studyD oth qulittive nd quntittiveD on the experimentl proxies of 2 nd order suseptiilities of BD Q nd SF he results elow ∼ 20 qeGe need however to e tken refullyD s iy show here some limits of ppliilityF

Comparison with enhanced proxies and conserved charges cumulants

king dvntge of the ft tht iy o'ers the possiility to get ess to ll prtiles produed in hevyEion ollisionsD s ould lulte the rtios of ext 2 nd orE der umulnts of onserved hrges using the nlysis desried in ppendix gF st hs een motivted y the ojetiveD explined in setion QFSD to ompre them with the enhned proxies proposed in PQR nd the one mesured y eD studied in the preE vious susetionF his wyD s n test if the proposed enhned proxiesD resulting from theoretil studyD re e'etively etter t reproduing umulnts of onserved hrges thn the ones used y eD vi dynmil simultions whih reretes the onditions of the experimentF he rtios of onserved hrge @oAvrines studied here re the following onesX

C QB = σ 11 QB σ 2 B ≡ χ QB 11 χ B 2 , C QS = σ 11 QS σ 2 S ≡ χ QS 11 χ S 2 , C BS = -σ 11 BS σ 2 S ≡ χ BS 11 χ S 2
. @SFPFQA IHP SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi he minus sign in the de(nition of C BS omes from the ft thtD when mesuring these onserved hrges from netEhdron multipliitiesD positive ryoni numer is ssoited to negtive strngeness s strnge ryons rry s qurks whih hve S = -1 y onventionF hese rtios reD so frD pproximted experimentlly with netEπD netEK nd netEp @oAvrines rtios mesured y eD relled here from eqution @PFQFIVAX

C Qp = σ 11 Qp σ 2 p ∼ = χ QB 11 χ B 2 , C QK = σ 11 QK σ 2 K ∼ = χ QS 11 χ S 2 , C pK = σ 11 pK σ 2 K ∼ = χ BS 11 χ S 2 .
he enhned proxies relted to the two strngenessErelted rtiosD presented in suE setion PFQFQ nd sed on vrines of netEKD ΛD Ξ nd ΩD re lso relled here from equtions @PFQFPSA nd @PFQFPTAX

CQS = 1 2 . σ 2 K σ 2 K + σ 2 Λ ∼ = χ QS 11 χ S 2 , CBS = σ 2 Λ σ 2 K + σ 2 Λ or C′ BS = σ 2 Λ + 2σ 2 Ξ + 3σ 2 Ω σ 2 Λ + 4σ 2 Ξ + 9σ 2 Ω + σ 2 K ∼ = -χ BS 11 χ S 2 .
roweverD no enhned proxy rtio hs een proposed for the QB orreltion @χ 11 QB /χ 2 B A in PQRD wheres it hs een mesured y the e ollortion vi C Qp F reneD s propose to study the following proxy rtioX

CQB = σ 11 πp + σ 2 p 2σ 2 p + σ 2 Λ ∼ = χ QB 11 χ B 2 .
@SFPFRA his proposition is sed on the rekdown of hdroni ontriution to χ BQ 11 nd χ B 2 D shown in (gure SFIHF st follows the rgument from the uthors sying thtD to uild good proxy rtioD it is importnt to use @oAvrine proxies tht re eqully good for oth numertor nd denomintorF roweverD when looking t those (guresD one n reE lise tht σ 2 p + σ 11 πp ontriute to igger frtion @< 1A of χ QB thn 2σ 2 p + σ 2 Λ ontriutes to χ B 2 F s ould hve proposed to use only σ 2 p s proxy for χ BQ 11 D to keep lmost equl ontriution proportionsF s still propose to use σ 11 πp in ddition to σ 2 p thoughD in order to follow the uthors9 lim tht isospin rndomistion prevents from uilding proxies with )ututions of netEp only PQRF feuse of isospin rndomistionD protons represent pproximtely hlf of the nuleons in the systemD wht justi(es then the ftor 2 in front of σ 2 p for the χ B IHQ grei SF fiew ixiq gex 8 h yp gwvex sr iy reneD ll these rtios hve een lulted from prtiles still mesured within |η| < 0.5 nd with 0.4 < p T < 1.6 qeD to mth with the mesurement of the e proxiesF he results s funtion of N part re displyed in (gure SFIID for the (ve sme energies from whih results of the previous susetion hve een shownF he (rst imE portnt onlusion from these results is tht the enhned proxiesD proposed in PQR nd denoted CXY @in lueGyn in the plotsAD re e'etively wy etter t reproduing the rtios of onserved hrges @oAvrines @in greenA thn the one used y e @in redAF sn prtiulrD the C BS rtios deserves speil ttention hereF es disussed lredy in susetion PFQFQD its proxy C pK mesured y e show ertin entrlity depenE dene elow IWFT qeGe whih is not present for higher ollision energiesD where it lso hnges its glol signF por wht n e oserved hereD the rtio C BS for ext hrges hs solutely no entrlity dependene exept for UFU qe where it opertes ler hnge of ehviourF sts vlue dereses from ultrEperipherl to peripherl eventsD nd then remins t n overll vlue onsistent with HD while it remins t HFP whtever the entrlity for ll energies oveF he results t √ s N N = 7.7 qeGe re lso the only ones for whih the enhned rtio CBS does not reprodue etter the rtio of onserved hrges thn C pK F roweverD results from the previous setions shown tht iy QFRSI simultions re not relly onsistent with experimentl dt t suh low energies of the fi progrmD so it is hrd to mke ny interprettion of these results spei(llyF yn di'erent levelD it is worth notiing tht no di'erene is visile etween the two enhned proxies CBS @involving only netEK nd netEΛ vrinesA nd C′ BS @involving in ddition netEΞ nd netEΩAF his oservtion is very interesting s it mens tht using only netEΛ vrine in ddition to the ones lredy mesured y e improves signi(E ntly the proxiesF his is true for the study of C BS in prtiulrD ut lso more generlly for ll 2 nd order umulnts of onserved hrgesD s the ryonEstrngeness orreltor is the only one where using Ξ nd Ω hs een proposedF reneD the C′ BS rtio is not relly useful s it does not ring nything more thn the CBS oneF gonsequentlyD CBS will e the only enhned proxy of C BS onsidered for the rest of my workD while C′ BS will not e used nymoreF IHR SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi he only enhned rtio sed on ovrine is the CQB proxy rtio proposed y myselfD using σ 11 πp F yne ould even do without thoughD s its mplitude is negligile omE pred to the one of σ 2 p with whih it is omined t the numertorD s seen from (gures SFU nd SFVF en importnt thing to notify then is the ft tht the enhned proxiesD whih show remrkle good greement with rtios of onserved hrgesD ontin only vrinesF his llows to redue drstilly the sttistil )ututions of otined rtiosD whih re minly originting from ovrines in the e proxies s n e seen in the previous susetionF he omprison etween the rtios of 2 nd order umulnts of BD Q nd SD their e proxies nd proposed enhned proxiesD ll of them lulted from iy QFRSI simuE ltionsD is summrised in (gure SFIPF ell the rtios re displyed there s funtion of the ollision energyD for the most entrl @HES7A nd most peripherl @UHEVH7A ollisions s onsidered in the nlysis mde y e in PIIF es lredy sttedD the ft tht the enhned proxies reprodues lmost perfetly the onserved hrges rtios is lerly visile thereF s rell tht experimentl dt from e re only displyed to ompre with e proxies lulted from simulted eventsD ut tht the min purpose is to see whih proxiesD etween the e ones nd the enhned onesD re the most similr to umulnts of onserved hrgesF he quntittive vritions of these rtios s funtion IHS grei SF fiew ixiq gex 8 h yp gwvex sr iy of the energy re nevertheless pretty identil from IWFT qeGe up to higher energiesD nd using either enhned proxies or e proxies does not mke ny di'ereneF felow IWFT qeGeD where signi(nt vritions of C BS nd C QS re oservedD the enhned proxies seem to show less pronouned hnges thn the e onesF roweverD one gin the results from iy in this energy rnge re found to diverge sustntilly from the experimentl dtD wht prevents to drw ny onlusionF 5.2.3 Impact of hadronic cascades on the 2 nd order cumulants he lst prt of my work onerns the impt of the hdroni phse t the end of rsgs on the oservles studied previouslyF huring these lst stgesD the hdrons formed from the ulk mtter will reEintert with eh other in suessive ollisionsD oth elsti nd inelstiD wht hnges oth the hemistry of the system nd the kinemti distriE utionsD until the freezeEouts hppenF reneD s s explined lredy in setion QFSD my ojetive is to study how the )ututions of onserved hrges imprinted in the distriuE tion of prtiles formed t hdronistion survive these hdroni sdesF sn prtiulrD s hve intended to quntify these hngesD in order to support the experimentl e'orts to proe those )ututions through the mesurement of netEmultipliity umulntsF o do soD s n tke dvntge of the modulr oneption of iyD whih llows to ess the distriution of prtiles efore they enter the rwh fterurner simulting these hdroni reEintertionsF The results calculated from full events are represented by full lines, while results calculated before hadronic cascades are represented by dotted lines.

s strted y looking t the impt of hdroni sdes on the @oAvrines of netE multipliity umulnts used to form the rtios of interestF sn (gure SFIQ re displyed σ 2 p D σ 2 π D σ 2 K nd σ 2 Λ lulted for prtiles t the end of omplete event simultions @referred to s 4full4 eventsA nd efore the hdroni sdes @designted y 4no hs4 in the plotsAF hese vrines re of interest s they re used in oth e proxies nd the IHT SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi proposed enhned proxiesD introdued in susetion PFQFQ nd disussed in the previous susetionF sn oth sesD efore hdroni sdes nd t the end of the eventsD they re lulted in the sme onditions thn the e mesurementsD i.e. for 0.4 < p T < 1.6 qe nd within |η| < 0.5F he prinipl onlusion oming from (gure SFIQ is the ft tht hdroni sdes re shown to hve strong impt on vrines of netEprtile multipliitiesF hey inrese gretly the signlD from douling to even tripling itD with di'erent mgnitudes depending on the hdroni speies thoughF he inrese of vrines of mesons @hrged π nd KA due to hdroni sdes tends to grow with energyF wenwhileD the proportion of signl for ryons @p nd ΛA due to hdroni sdes dereses from UFU qeGe to PU qeGe while inreses gin when going up to PHH qeGeF he sme onlusion is lso visile for the ovrinesD shown in (gure SFIR for full events nd efore hdroni sdes s wellF rere ginD gret prt of the signl seem to originte from the hdroni phse for ll three ovrines studiedF sn ftD for ll ovrines results shown hereD hdroni sdes re responsile for most of the ovrine mplitudeD if not ll of itD s seen despite the importnt sttistil )ututionsF Figure 5.14: Covariances of net-p, net-π and net-K multiplicity distribution vs. N part for dierent energies, obtained from EPOS 3.451 simulations and compared with STAR results (dots) [211]. The results calculated from full events are represented by full lines, while results calculated before hadronic cascades are represented by dotted lines.

he inrese of the vrines nd ovrines n e explined y the ft thtD durE ing the hdroni sdesD the numerous inelsti stterings tht our produes mny more of the involved hdroni speiesD oupled to the suessive deys of hevy resoE nnes produed t hdronistionF reneD the suessive deys nd inelsti stteringsD produing simultneously severl of the hdroni speies of interestD led unvoidly to the mpli(tion the orreltions rried y @oAvrinesD lurring this wy the rel mE plitude of the therml )ututions of interestF enother e'et whih might ply role here is the kinemti spredingD or the ft tht prtiles rrying onserved hrges might ontminte the phse spe onsidered in the nlysis while not originting from there originllyF owrds ontmintion of the η window studiedD we n nively postulte tht the numer of onserved hrges @rried y hdronsA entering the onsidered windowD during the hdroni sdesD is ounterlned y the sme hrges going out during this sme phseF he sttement mde from the results exposed here supports strongly IHU grei SF fiew ixiq gex 8 h yp gwvex sr iy the results from study led with hyrid version of rwhD whih hs een oupled to )uid dynmil simultion of ulk mtter PQIF hey investigted the timeEevolution of the orreltion of distriutions of hdron fmilies rrying onserved hrgesD with regrd to these sme distriution t hdronistion timeF he onlusion ws tht the (nl distriution of hdrons oserved y experiments is not relly relted nymore to the one otined fter hdronistionD whih is ontining the potentil ritil signl from phse trnsitionF sn other wordsD ny informtion enoded in the kinemti distriution of hdrons t hdronistion time is not re)eted in the distriution t the very end of the ollisionD euse hdroni restterings deorrelte signi(ntly these distriutionsF he seond step eing to hve look t the proxy rtiosD s show in (gure SFIS the results otined for onserved hrges nd oth e nd enhned proxies s funE tion of √ s N N D for full events nd efore hdroni sdesF rereD lmost ll rtios show very smll vrition etween efore nd fter hdroni sdesD exept CBS whih vlue is pproximtely douled y hdroni sdes for oth entrl nd peripherl entrlity lssesF st on(rms thusD with wht n e oserved from the vrines nd ovrines used to uild these proxy rtiosD tht the pprent smll modi(tion due to the hdroni phse do not men tht it hs negligile imptF yn the ontrryD the IHV SFPF h yp ri 2 nd yhi gwvex yp gyxiih greqi results on other rtios just re)et inidentlly the ft tht proxies used in numertor nd denomintor re modi(ed in the sme proportions during hdroni sdesF por ext onserved hrges howeverD the smll modi(tions of rtios re truly due to smll modi(tions of the onserved hrges @oAvrines used y hdroni sdesD thnks to the preutions tken in the nlysis whih is exposed in ppendix gF he impt of hdroni sdes on vrines nd ovrines of onserved hrges for the simulted events used in this work n e seen in (gures hFI nd hFPD respetivelyF elthough it is di0ultD s it stndsD to quntify the impt of hdroni sdes on e proxy rtios due to the lrge sttistil )ututions of ovrines @see (gure SFIRAD s n still legitimtely try to quntify it on enhned proxies nd onserved hrge rtiosF gonsequentlyD the rtios of C XY nd ssoited proxies CXY efore hdroni sdes over the vlues for full events re shown in (gure SFITF xote tht even though s m tlking out quntifying the impt of hdroni sdesD s do represent hereD vi these rtiosD the proportion of the signl mesured in the end of the ollision whih e'etively origintes from hdronistionF he most importnt modi(tion of the signl is otined for the CBS proxyD s mentioned in the disussion of the previous (gureF ynly SH to TH7 of the (nl mesured proxy is e'etively oming from efore hdroni sdeF gontrry to this proxyD the orresponding ext rtio C BS hs proportion of signl from hdroE IHW grei SF fiew ixiq gex 8 h yp gwvex sr iy nistion vrying from ∼ 1.2 in entrl ollisions to ∼ 1 in peripherl onesF et low energyD it even shows strong vritionsD whih n however hrdly e interpreted s disussed severl time lredyF por the two other orreltors relted to QD n interesting point to notie is tht even though their modi(tion ftors due to hdroni sdes do not hve the sme mplitudeD they hve pproximtely similr vritions with energyF hose proportion of signl originting from efore the hdroni sdes re roughly vrying etween ∼ 0.8 nd ∼ 1 for ext rtios C QS nd C QB D while vrying etween ∼ 1 nd ∼ 1.2 for enhned proxies CQS nd CQB F Figure 5.17: Core proportion of C XY and enhanced proxies CXY ratios over the total value calculated before hadronic cascades, plotted as a function of √ s N N for central (left) and peripheral collisions (right).

et lstD it is importnt to see how muh of the signl efore hdroni sdes is relly oming from the )uid itselfD identi(ed y the ore in iy frmeworkF reneD (gure SFIU show the rtio etween proxy nd onserved hrges rtios originting from the oreD over their totl vlues efore hdroni sdesF hese rtio re ll very lose to I ove ∼ 15 qeGeD ut diverge from this vlue t low ollision energiesF his result ws expetedD s previous study onduted with iy on the origin of produed prtilesD mde vi p T distriution for fi euEeu ollisionsD hs shown tht the vst mjority of lowEp T hdrons re originting from the ore PWHF por low energy howeverD the ore is supposed to represent smller prt of the systemD s it is hrder to reh the ritil energy density to form itD wht explins the oserved devition to IF IIH SFQF wwe yp iv yx 2 nd yhi gwvex h 5.3 Summary of results on 2 nd order cumulants study fefore moving on to the generl onlusion of the thesisD s will summrise the results otined in this hpterD sed on the ojetives outlined in setion QFSF es reminderD ll the work presented here is relted to euEeu ollisions performed in the energy rnge of the fi progrmD i.e. √ s N N = 7.7D IIFSD IRFSD IWFTD PUD QWD TPFR nd PHH qe here in prtiulrF sn the (rst setionD s hve exposed some results onerning prtile prodution of ommonly mesured hdroni speies from simultions otined with iy QFRSID one of the ltest versions of the iqF o otin themD n importnt work hs een neessry to ollet the experimentl dt to ompre withD nd to write the orresponding nlyses using the iy nlysis frmeworkF he new mhinery s hve developed y integrting the use of ivet in this nlysis frmeworkD presented in hpter RD ould only e used for one of these nlysesF iven if we ould hve used ivet to write the nlyses we wnted to pply on our simultions whih were not ville yetD the system ntively ville in iy is more onvenient to use s most of the lssil distriutions usully mesured re lredy enoded into routinesF elthough we were limited in employing ivetD euse of the smll numer of nlyses for euEeu ollisions ville for the fi so frD it shown tht this new feture hs een suessfully integrted nd is now funtionlF he results for prtile prodution onsist of hrged prtiles pseudorpidity distriutions for lrge eptneD nd p T spetr in the low momentum rnge @0 < p T < 2 qeA for identi(ed light hdrons @π ± D K ± D p/pA nd strnge ryons @Λ/ ΛD Ξ -/ Ξ+ D Ω -/ Ω+ AF sn the phse spe of interest for my next studyD i.e. for p T < 2 qe nd t entrl pseudorpidity |η| < 0.5D iy hs een shown to reprodue very well prtile prodution in overllF st is espeilly the se for ollisions energies ove PH qeGeD while under this sleD the results show more nd more importnt disrepnies with the experimentl mesurements s ollision energy deresesF his result ws nevertheless expetedD euse of the importnt ssumption on whih relies the rtonEfsed qriovEegge heory used in iyD tht initil intertions hppens ll instntneouslyF fy exploring this energy rngeD we re in ft testing the limits of iy ppliilityD s it ws originlly designed to e minly pplied to the physis of the vrgF es it hs een proven to reprodue properly experimentl dt in generlD s hve then employed iy QFRSI to study the 2 nd order umulnts of onserved hrges BD QD S nd its proxies used in experiments in the seond setionF s strted y ompring the results on vrines nd ovrines of netEmultipliity distriutions for protonsD pions nd kons to the dt from the e ollortionF esults for @oAvrines of netEpD netEπD netEK nd their rtios from iy simulE tions re in good qulittive greementD nd even quntittive glollyD with e mesurements for ollisions energies ove ∼ 20 qeGeF por low energies howeverD iy results show slightly di'erent qulittive ehviourD re)eting its di0ulties to reprodue properly prtile produtionD pointed out in the previous prgrphsF III grei SF fiew ixiq gex 8 h yp gwvex sr iy s hve then mesured from iy simultions some enhned proxy rtios sed on vriE nes of netEΛD netEΞ nd netEΩ in dditionD proposed y the uthors of PQR nd myselfD who hve een inspired y their studyF foth proxy rtiosD with the ones mesured y eD were ompred to the @oAvrines rtios of ext onserved hrgesD to evlute how e'etive re the former ones to pproximte the ltter onesF st ppers tht proxy rtios CQS nd CBS D proposed in PQRD nd CQB proposed y myself thnks to this ited workD re wy etter t reproduing the onserved hrge rtios thn the e proxiesF sn prtiulrD the only use of netEΛ vrineD in ddition to the usul netEpD netEπ nd netEK vrinesD improve lredy gretly the e0ieny of the proxies to reprodues the ext rtiosF woreoverD using only vrines ppers to e su0ient to uild good proxiesD s protonsD kons nd lmds rry eh of them two di'erent onserved hrgesD wht redues gretly the sttistil )ututions on the rtiosF enother mesure of oth proxy nd ext rtios just fter hdronistion of the simulted systemD mde possile y the modulr oneption of iyD hve llowed me to quntify the impt of hdroni sdes on these oservlesF upporting the onlusion from previous studiesD it ppers tht the hdroni reE sttering stge of the ollision modi(es importntly the signl of netEmultipliity )ututionsF elthough hdroni sdes hve lrge in)uene on the mplitude of the netEmultipliity @oAvrinesD the proxy rtios uilt out of them seem to e little 'eted y hdroni sdesF CQS nd CQB in prtiulr su'er very smll quntittive modi(tions due to the hdroni stgeD so they n e used s good proxies to proe their orresponding onserved hrges rtiosF he CBS proxy rtioD thoughD do not shre this property nd mkes d proxy in tht senseF pinllyD s ould estimte the proportion of )ututions originting from the ore itself efore hdronistionD for rtios of onserved hrges nd proxiesF s expeted tht most of the signl should ome from the oreD whih evolves like n lmost perfet )uid in iy to mimi the ehviour of qF reedent work hd in ft demonstrted tht s the vst mjority of lowEp T prtiles t midErpidity re produed y the hdronistion of this ulk mtterF wy results on(rmed tht the )ututions mesured fter hdronistion in the phse spe onsidered @0.4 < p T < 1.6 qe for |η| < 0.5A re lmost exlusively originting from the oreD exept t the lowest energies onsidered where the ulk mtter represent smller frtion of the system retedF IIP CONCLUSION & OUTLOOK he min gol of my reserhD presented in this thesisD ws to study the impt of hdroni sdes on the 2 nd order umulnts of netEmultipliity distriutions @lso lled vrines nd ovrinesAD for di'erent proxies of onserved hrges BD Q nd SF he min motivtions for this work hve een exposed in the end of hpter PD following detiled desription of the ontext disussed in the previous prgrphsD fter hving depited in hpter I the min kground in whih it tkes pleD i.e. the w of prE tile physisF st is sed in prtiulr on the mesurement of netEπD netEK nd netEp @oAvrines y the e ollortion PIID nd the proposition of enhned proxies employing dditionlly netEΛD netEΞ nd netEΩ vrines from study omining lttie quntum hromodynmis nd rq model lultions PQRF o ondut this reserhD s hve used the iy generl purpose event genertorD priniplly dedited to the study of rsgsF st llows to study properly the eventEyEevent )ututions of onserved hrges y simultingD one y oneD the omplete dynmis of ollisionsD reproduing the onditions of the experimentsF st fetures notlyD mong mny other hrteristis introdued in hpter QD oreEoron seprtion of mtterD with the densest prt @oreA treted s nerEperfet )uid to mimi the expeted ehviour of the evolution of qF his spei(ity mkes it very suessful to reprodue mny results from the experiments towrd the study of the qF he modulr oneption of iy provides ess to the prtiles distriutions just fter hdronistionD wht mkes it tool of hoie for my workF woreoverD the oreEoron feture enles to identify whih hdrons originte from the oreD hene whih prt of the )ututions of onserved hrges they rry relly omes e'etively from qF his study tkes ple in the proess of vlidtion for iy RD new version of the event genertor relesed pulily reently PTVF heres it ws initilly developed minly to study the physis of the vrgD in the rnge of the eGe in ollision energyD some new hnges in the models it uses mkes it now legitimtely pplile to the fi progrmD down to ertin given energy PTWF his limit of ppliilityD inherent to the min theoretil piee on whih iy reliesD is expeted round ∼ 20 qeGeD ut one needs in ny se to test it y ompring simultion results with experimentl dtF sn order to help in this proessD s hve dpted iy to mke it omptile with ivetD n nlysis toolkit uilt to systemtise the omprison etween experimentl dt nd iq simultionsD s detiled in hpter RF his new feture is of ourse useful to ll poE tentil future usersD s it will llow to ompre esily nd diretly the simultions from iy to dt for whih the nlysis is villeF fut it lso rings signi(nt help to the developers of iqsD s it o'ers n experimentl dt lirry delivered with the ssoited nlysisX for this resonD s hve developed n ensemle of odes to inlude the possiility to ll ivet diretly from iy9 own nlysis frmeworkF xeverthelessD IIQ gyxgvsyx 8 yvyyu despite eing fully funtionlD this upgrde is limited y the ville nlyses in ivet regrding rsgsD nd more preisely for the fi whih is the energy rnge of interest for my workF por this resonD s hd to write mny nlyses nd ollet the orresponding dt to test iy QFRSID one of the lst nd most dvned etEversion of iy RD ginst experimentl mesurementsF elthough the new feture with ivet feture hs not een muh used for the next studyD it still helped into heking prtile prodution for the simulted ollisions of interestD s well s heking the vlidity of my nlysis methodF he (rst step of my work exposed in hpter S hs een to hek prtile prodution in the phse spe of interest for the mesurement of umulntsF rving looked t p T spetr for light hdrons π ± D K ± D p/p nd @ntiAhyperons ΛD Ξ -nd Ω -D in ddition to the pseudorpidity distriution of hrged prtilesD it ppers tht iy simultions re overll in very good greement with experimentl dt for euEeu ollisions down to ∼ 20 qeGeF felow these energiesD s expetedD the p T spetr strt to devite from the mesurementsD y getting steeper slopes s onsequene of the hypothesis of siE multneous initil intertions of the fqF iven though the disrepnies re not drmtiD nd iy displyed results remins resonly lose to the dt in the sruE tinised kinemti rnge @p T < 2 qe t |η| < 0.5AD this lerly on(rms our expettions nd estlishes in some wy limit of pplition for the iqF sn the seond prt of hpter SD s hve displyed (rst of ll the results from iy omE pred with e mesurements of netEpD netEπ nd netEK @oAvrines nd their rtiosF hespite the pretty importnt sttistil )ututions of my results for the ovrinesD due to insu0ient simultions sttistisD iy is le to properly reprodue the experimentl dt in oth qulittive nd quntittive wysD ove ∼ 20 qeGeF et lower energiesD the shpe of iy results devites from the expeted liner inresing with deresing entrlityD wht simply re)ets the limits oserved in prtile produtionF henD s hve ompred the rtios of @oAvrines of onserved hrges with the orresponding e proxy rtios nd the proposed enhned proxy rtiosF hese omprisons demonstrte thtD for prtile distriution in the (nl stteD the proposed enhned proxy rtios do e'etively reprodue muh etter the results for ext onserved hrges thn the ones employed y eD in the rnge where iy reprodues orretly prtile produtionF es mtter of ftD it shows tht the dditionl use of netEΛ vrines lone improves drstilly the qulity of the proxiesF his is very enourging (ndingD s the e ollortion hs reently pulished results for the mesurement of umulnts for netEΛ distriutions t severl di'erent orders PIPD mening tht they ould mesure these enhned proxy rtiosX

CQS = 1 2 . σ 2 K σ 2 K + σ 2 Λ , CBS = σ 2 Λ σ 2 K + σ 2 Λ , CQB = σ 11 πp + σ 2 p 2σ 2 p + σ 2 Λ .
enother importnt tkewy messge in ddition is the ft tht the use of ovrines is solutely not neessry to uild good proxy rtiosF et the exeption of the CQB proxy rtio proposed y myselfD whih employs σ 11 πp @even though its impt on the rtio is lmost negligile ompred to σ 2 p AD vrines re enoughF sndeedD mny hdroni speies rry two onserved hrges t oneD like p for B nd Q or Λ for B nd SD wht mkes them lone very good proes for orreltions etween di'erent hrgesF henD s hve shown the impt of the hdroni sdes on the @oAvrines studiedD y lulting them from the prtile distriutions just fter hdronistionF por onE served hrgesD the rtios re left unhnged efore nd fter hdroni sdesD s the @oAvrines of B, Q, S re lmost not impted y this reEintertion phseF iven if it IIR gyxgvsyx 8 yvyyu ws expeted from hrges whih re supposed to e onservedD it proves t lest tht kinemti spreding or feedEdown from hevier resonnes @for S in prtiulrA do not ply n importnt roleF yn the ontrryD the @oAvrines of netEprtile distriution re highly impted y the hdroni stgeD whih mpli(es their signl y ftors P to R omE pred to the mesurements fter hdronistionF xeverthelessD most of the proxy rtios re little modi(ed y the hdroni sdesD s oth their numertors nd denomintors seem to e impted in the sme wyD exept for the enhned proxy CBS F elthough the ltter is in very good greement with the onserved hrges rtio C BS for omplete eventsD it does not reprodue quntittively well C BS efore hdroni sdesD even if quntittively loser to it thn the e proxy C pK F roweverD to form good proxyD rtio should not e too muh impted y the hdroni sdesD to re)et s muh s possile its vlue efore fter hdronistionF pinllyD s hve estimted the proportion of the signl originting from the oreD for oth rtios of onserved hrge @oAvrines nd orresponding enhned proxiesF et lowEp T nd entrl @pseudoArpidityD the mjority of prtiles is produed from the ore @orD in more physil pitureD the qAF husD the signl of )ututions from netEhrges nd their proxies eing mesured in this kinemti rnge omes lmost exlusively from the oreF ynly for the low energiesD this proportion devites from oneD s the dense mtter represents smller prt of the system reted in the ollisionF his is n importnt results whih mens thtD in the phse spe where the )ututions of netEprtiles re proedD there is very few ontmintion from the hdrons whih re not originting from ulk mtterD nd whih onsequently did not rry ny mrk of the potentil ritil )ututionsF he onlusions from this work re very importnt s they shed light on signi(nt e'ets on the experimentl oservles used to proe the presene of giF woreoverD using iq simultions llows to quntify how the lst stges of the ollisions modify the signl of interestD s )ututions of severl ntures emerge from di'erent soures in the omplex evolution of systems reted in rsgsF xeverthelessD this work ould e led even furtherF es (rst simple stepD the sttistil )ututions of the ovrines in prtiulr ould e redued y simulting more onsequent numer of eventsF henD it ould lso e good to try to (ndD for C BS D proxy whih would reprodue it quntittively oth fter hdronistion nd in the (nl stteD s the CBS one does only ful(ll its mission in the lst seF iventullyD nd most importntlyD this study ould lso e pplied to higher order umulnts of netEprtile multipliityD whih re lso mesured experimentlly PIPD PIRD PPHD QITF es they re expeted to e even more sensitive to the presene of ritility thn the 2 nd order onesD it would e very interesting to see if the enhned proxy rtios disussed in this thesis reprodue s well their orresponding rtios of onserved hrges t higher ordersF sn this ppendixD s will explin rie)y how the nlysis for lulting umulnts of netEmultipliity distriutionsD from 1 st to 4 th orderD hve een implemented in iyD efore to list ll the di'erent prmeters nd detil its funtioningF sn seond timeD s will disply simple exmple of the instrutions neessry to lulte netEmultipliity 2 nd order umulnt with the iy nlysis frmeworkF hese nlyses re the one whih hve een used to otin the results shown in setion SFPF C.1 Technical implementation of the analysis he ode neessry to lulte the moments of netEmultipliity distriutionD used in the lultion of umulntsD hve een inorported in the preEexistent nlysis frmeE work of iy presented in susetion RFPFQF ell these implementtions hve een mde in the (le $EPO/KW/xan.fF s strted with enling the 4xtrans()4 suroutineD responsile for the reding of .optns (les nd interprettion of the instrutions written withinD to understnd the new vrile reted to ll the umulnts nlysisF his new vrileD whih s hve nmed 4ncum-evt4D n used s funtion of ny event vrile like the ollision energyD the numer of prtiipnts N part D or the hrged multipliity for instneF s hve de(ned the suroutine responsile for the umulnts lultionD 4mupurp\_susc()4D s multiE purpose nlysis oneD i.e. suroutine tking input prmeters in ddition to ll the generi ones introdued in susetion RFPFQF reneD s hd to dpt the orresponding suroutine 4mupurp()4 y dding new identi(erD IHHTD whih lls 4mupurp\_susc()4 when used with 4xpara()4D the funtion storing the dditionl input prmetersF pinllyD one the ode of the nlysis suroutine itself hd een implementedD s just needed to ensure tht the results were properly trnsmittedD vi the 4ypara()4 funE tion storing themD to the .histo (leF o do soD s dded the pproprite instrutions in the 4xval()4 suroutineD in hrge of ssigning to the histogrm ins the vlue of the orresponding oservle lulted over the eventF IPW eixhs gF xiEwvsvsgs gwvex exevs sx iy C.2 Structure of the analysis routine he ses of the nlysis re of ourse the input prmetersD tht s will detil in (rstF es explined previouslyD they re provided to the 4mupurp\_susc()4 suroutine vi the 4xpara()4 funtionD whose di'erent elements re expeted to ontin the following inE formtion @4n4 simple refers here to the histogrm numerAF he expeted prmeter to e used nd their possile vlues re summed up in the tle gFIF he lst prmeter will inditeD y its lengthD the order of the moment to e luE ltedD nd the hrges or prtiles to onsider y the digits it is mde ofF he orresponE dene etween the digits nd the ssoited netEhrge or netEprtile numer is given in tle gFPF a, b, c, d

I P Q R S T U V W ghrgeGprtile B Q S π K p Λ Ξ Ω Table C
.2: Correspondence between digits and associated charge or particle for xpara (9,n).

elthough the study presented in this thesis fous on the 2 nd order umulntsD whih require oth 1 st nd 2 nd order moments of netEmultipliity distriution to e lultedD s hve developed the suroutine with the ility to lulte moments up to the 4 th orderF woreoverD it ws oneived in wy tht only few modi(tions re neessry to enle it to lulte even higher order momentsF IQH gFPF gi yp ri exevs ysxi efter hving treted properly the input prmetersD the suroutine will perform loop over the prtiles of the event nlysedD nd selet only the prtiles ful(lling the riteri estlishedF ht is to syD it will onsider either p prtiles nd their prents or prtiles efore hdroni sdesD pply either strit feedEdown orretionD hge riteri or no orretion t llD nd onsider either ll prtiles or prtiles oming exluE sively from the ore or oron prtF he lultion of the moment of netEhrgeGprtile will then vryD following whih hrge or prtile hs een hosenF sn the se of ryoni numer B or eletri hrge QD s the gol would e to ompre these netEhrge umulnts with the netEprtile umulnts used s proxies y the experimentD the nlysis hs to e s lose s possile to the netEprtile seF reneD s in the ltter se the hge ut is often usedD the netEhrges onsidered will e lulted t the primry prtile level @iFeF efore deys of prtilesAD nd not t the p levelF st ould legitimtely e done t the p levelD s Q nd B re onserved in wek deysF roweverD we ensure y doing so to onsider the netEhrge of the phse spe of interest @ysA without ny loss or gin due to kinemti spredingD iFeF the loss of hrge due to dughter prtiles going out of the ys while their prents were inF st prevents equllyD on the ontrryD from ounting the hrge of dughter prtiles whih re in the ysD while their prents were outF sn order to void douleEountingD the prtiles hving the required sttus will only hve their B or Q hrge ounted if their prents does not hve the required sttusD s the hrge of the ltter would hve een ounted lredy otherwiseF por netEB lultionD the di'erene etween qurks nd ntiqurks δq i = n q i -n q i is heked for eh prtile iD nd the netEB vlue is dded to the totl one δB (0,N ptl ) X δB (0,i) = δB (0,i-1) + δq i ÷ 3 , @gFPFIA with ÷ symolising the quotient of euliden divisionF hus δq i ÷3 = ±1 for @ntiAryonsD nd is null for mesons @no tetrGpentqurks de(ned in iyAF por netEQ lultionD the hrge Q i is heked for eh prtile i nd simply dded to the totl netEQ vlue δQ (0,N ptl ) X δQ (0,i) = δQ (0,i-1) + Q i . @gFPFPA sn ddition to the prolem of kinemti spreding desried for netEB nd netEQ lultionsD stle p prtiles nnot e onsidered lone for netES lultionD s strngeness is not onserved y the wek intertionF gonsequentlyD it would e wshed out y suessive wek deysD unless using the 4nodecay4 instrution for the wek deying prtiles like ΛD ΣD ΞD Ω or K 0 s F roweverD the im of this nlysis is to void suh onstrints s muh s possileF he simple strtegy s used to limit this prolem onsists of ignoring ll prtiles for whih the prent mthes the required sttusD without ny kinemti onsidertionF sn other wordsD only the (rst prtiles with the required sttus within the ys re ounted nd their dughter ignoredD similrly to the netE B/Q seD in order to void doule ountingD kinemti spreding ut lso potentil ontmintion from c/b wek feedEdownF sn the endD in order to lulte netESD the netEnumer of strnge qurks δs i = n s i -n s i omposing eh prtile i is sustrted to the totl netES vlue δS (0,N ptl ) X δS (0,i) = δS (0,i-1) -δs i , @gFPFQA s positive strngeness is ssoited to s qurks y onventionD so δs i = -S i F IQI eixhs gF xiEwvsvsgs gwvex exevs sx iy pinllyD to lulte the netEnumer of identi(ed prtiles X ID D the only ingredient to tke into ount in ddition to the sttus nd origin of prtilesD like for the onserved hrgesD is the feedEdown orretionF hepending on the user9s hoieD the feedEdown ontriution n e orreted either following the hge seletion method @hge< 1m hereD to mth with e de(nitionAD or with strit rejetion of ll prtiles oming from wek deysF sn the ltter seD whih orresponds to 4noweak4 in the iy nlysis lngugeD the prtiles from whih ll dughter prtiles re ignored re the K 0 s D ΛD Σ -/0/+ D Ξ -/0 nd Ω -D nd the ssoited ntiEprtilesF trightEforwrdlyD the totl netEX ID vlue ∆X (0,i) is lulted y dding +1 for prtiles @or positively hrged mesonsD y onventionA nd -1 for ntiEprtiles @negtively hrged mesonsAX ∆X (0,i) = ∆X (0,i-1) ± 1 .

@gFPFRA et lstD one the loop over prtiles is hievedD the di'erent netEhrgeGprtile numers re multiplied with eh other in the se of moment of order > 1D nd the result is stored in the 4ypara()4 funtionF he opertion is then repeted for eh event nlysedF C.3 Writing a net-multiplicity cumulant analysis sn this lst susetionD s will show expliitly the instrutions to write in n .optns he 4npnevt4 refers here to N part D nd 4ncum-evt4 to the nlysis for umulnts desried in the lst setionF he normlistion ftor 4R4 indites to verge the oservle over the events nlysedD nd the following numers tht it will e divided into RH ins etween N part = 0 nd N part = 400F he numer 4W4 fter 4xparas4 is just here to speify tht there will e nine input prmetersD whih orrespond to the ones desried in tle gFIF reneD the nlysis written here will lulte ⟨δN p ⟩ for p @ntiAprotons from ll originsD with 0.4 < p T < 1.6 qe nd within |η| < 0.5F he distriution is orreted from feedEdown y seleting the @ntiAprotons with hge< 1mD nd lulted s funtion of N part from H to RHH with ins of width ∆N part = 10 for events in the entrlity rnge HEVH7F gette dernière nnexe résumeD en frnçisD les trvux présentés préédemment dns e mnusritF hns un premier temps ser rppeléD dns l setion iFID le ontexte de es trvuxD suivi d9une présenttion du générteur d9événements iy qui en fut l9outil priniplD ouvrnt insi le ontenu des hpitres ID P et QF ves motivtions et ojetifs ynt guidé es trvuxD énonés dns l setion QFSD seront lors présentés dns l setion iFPF ves développements tehniques e'etués sur iy R dns le dre de ette thèseD disutés dns le hpitre RD seront dérits dns l setion iFQF v9étude exposée dns le hpitre S ser ensuite ordée dns l setion iFRD se lôturnt sur une disussion des potentielles perspetives envisgeles (n de poursuivre es trvuxF E.1 Contexte et motivations ves trvux présentés dns ette thèse s9insrivent dns l9étude du wodèle tnE drd @wA de l physique des prtiulesF gette théorie dérit omment les prtiules élémentires omposnt l mtière intergissent pr l9intermédiire des fores életroE mgnétiqueD file et forteF v (gure IFI représente insi les di'érentes prtiules le omposntD séprées en deux grndes fmilles X les fermionsD prtiules de mtièreD et les osonsD méditeurs d9intertionF v9intertion forteD exprimée sous l forme d9une théorie quntique des hmps portnt le nom de hromodynmique quntique @ghAD à use de l hrge dite de ouleur qui lui est propreD git sur les qurks et est trnsmise pr l9éhnge de gluonsF ne des rtéristiques mjeures de l ghD le 4on(nement de ouleur4D se trduit pr le fit qu9uune prtiule portnt une hrge de ouleur ne peut être oservée seule en onditions normles de densité et tempértureF einsiD les qurks sont toujours regroupés (n de former des ojets neutres en terme de hrge de ouleurD ppelés hdronsF r trois @qqqAD ils forment les ryonsD tels que les nuléons omposnt le noyu de l9tomeD ou pr pire de qurkEntiqurk @qEqA des mésonsD tels que les pions ou konsF IQU eixhs iF ÉwÉ pexÇes hi ve rÈi sl ependnt été prédit que sous des onditions extrêmes de très hute tempérture etGou densitéD un gz de hdrons devrit trnsitionner vers un nouvel étt de mtière où les qurks et gluons sont déon(nésD et pprissent omme lires visEàEvis de l9intertion forte X le plsm de qurks et gluons @qAF tmes fjörken propos lors que ette phseD dns lquelle l9nivers se serit trouvé quelques miroEseondes près le figEfngD pourE rit être reréée dns des ollisions d9ions lourds @gsvA ux énergies ultrEreltivistesF v (gure PFI illustre l9évolution du système réé dns de telles ollisions sur un diE grmme d9espeEtempsD où le q est supposé exister le temps d9une dizine de fmGD soit ∼ 10 -22 sF v9étude du digrmme de phse de l mtière nuléire motiv lors une ommunuté grndissnte de herheurFseFs à mettre en ple des expérienes pour étudier es gsvD e qui pouss à l rétion d9élérteurs de prtiules tels que le et le vrg u gixD ou ien le rsg u fxvF sl fut (nlement nnoné en PHHS que l rétion du q dns des ollisions euEeu vit été oservée onjointement pr les expérienes du rsgD ien qu9il fut pulié a posteriori qu9un tel étt de mtière vit déjà été réé uprvnt dns des ollisions E rélisées u F ur le pln théoriqueD l9étude du digrmme de phse est ependnt rendue di0ile pr une seonde propriété importnte de l gh X le fit que s onstnte de ouplge α s D mesurnt l9intensité de son intertionD ne soit en rélité ps onstnteF gette dernière vrie en fontion de l9éhelle d9énergie Q 2 impliquée dns l9intertion onsidéréeD omme illustré dns l (gure IFQF À sse énergieD l reltivement grnde vleur de α s (Q 2 ) enE trve l9utilistion de méthodes perturtivesD qui ne peuvent être ppliquées qu9à hute énergie où son intensité déroît symptotiquementF sl est insi impossile de résoudre nlytiquement l théorie à file tempérture T et potentiel himique ryonique µ B D et don d9étlir diretement une éqution d9étt ouvrnt ette région du digrmmeF ne pprohe nonEperturtive de l ghD onsistnt à disrétiser l9espeEtemps en un réseu où les qurks sont plés sur les sommets et les gluons sur les rêtesD permet nénmoins de luler des grndeurs thermodynmiques à prtir des premiers prinipesF fien que restreinte initilement u domine où µ B ≈ 0D l9utilistion de l gh sur réseu donn lieu à l prédition d9une trnsition de phse ontinue @dite crossoverA entre les phses de gz hdronique et le qD à petites vleurs de µ B F gel semle ujourd9hui on(rmé pr les résultts de gsv e'etuées à très hute énergie u vrg depuis PHIID exE plornt ette région spéi(que du digrmme de phseF lusieurs utres modèlesD sés sur des premiers prinipes de l ghD ont qunt à eux émis l9hypothèse de l9existene d9une trnsition de phse de 1 er ordre entre l mtière hdronique et le q à file T et à µ B (niF gette trnsition de phse impliquerit lors l présene d9un point ritique @gA à l jontion de ette trnsition ve le crossoverF v reherhe de e g est don l motivtion priniple du trvil présenté dns ette thèseD sé sur les motivtions qui seront détillées à l (n de ette setionF ne vision shémtique du digrmme de phse de l mtière nuléireD résumnt l9ensemle des points mentionnés préédemmentD est présentée dns l (gure PFQF v9existene d9une phse de superondutivité de ouleurD nlogue à l théorie de l supronduE tivité életromgnétique pour des hrges de ouleurD fut églement onjeturée dns l région de sse tempérture et de hut potentiel himique ryoniqueF hns l reherhe du point ritiqueD les suseptiilités thermodynmiques des hrges onservées @nomre ryonique BD hrge életrique Q et étrngeté SA sont des quntités théoriques très lrgement utiliséesF illes qunti(ent l9mplitude des hngements dns l fontion de prtition thermodynmique du systèmeD dues ux vritions de potentiels himiques des hrges onservéesD utrement dit les )ututions desdites hrgesF yrD es IQV iFIF gyxii i wysesyx )ututions sont supposées diverger dns un système suissnt des phénomènes ritiquesD i.e. dont les onditions s9pprohent de elles du gD e qui en font don des outils de hoixF ves suseptiilités sont églement reliées ux di'érents moments sttistiques des distriutions de vleurs nettes des hrges onservéesF in prtiulierD les suseptiilitées du 2 nd ordre sont reliées ux @oAvrines des distriutions de hrges orrespondntes @voir équtions @PFQFIPA et @PFQFIQAAF hu point de vue expérimentlD l reherhe du g est un des ojetifs mjeurs du progrmme fiD vi un sn du digrmme de phse en étudint des ollisions euEeu à di'érentes énergiesF in e'etD lors que le système réé dns des ollisions ve une énergie √ s N N > 100 qeGe dérit une trjetoire très prohe de µ B ≈ 0 dns le digrmme de phseD diminuer l9énergie de l ollision ugE mente les vleurs de µ B tteintes pr le systèmeF wesurer les )ututions de hrges onservées pour des ollisions à di'érentes énergies devrit don permettre d9identi(er quel système expérimente des e'ets ritiquesD en s de divergenes de es oservles omprées à des référenes étlies en l9sene de ritilitéF gependntD de nomreux éléments rendent ette étude omplexeD de pr les di'érenes fondmentles entre le dre théorique dns lequel les préditions sont réliséesD et le dre expérimentl dns lequel les oservles orrespondntes sont mesuréesF sl est noE tmment impossile de mesurer expérimentlement les hrges onservéesD puisqu9elles sont portées pr di'érentes espèes hdroniques qui ne sont ps toutes identi(les pr les déteteurs utilisésF v9utilistion de fmilles de prtiules de prourtion @ou prox-iesA pour mesurer les distriutions de BD Q et S dns les gsv est don indispensleD mis il est lors néessire de omprendre à quel point es proxies re)ètent e'etivement le omportement des hrges qu9elles sont ensées représenterF he plusD de nomreux phénomènes dns les gsv sont soures de )ututionsD et il est importnt d9essyer de démêler les )ututions dites 4thermles4D qui portent l tre d9une potentielle ritilE itéD des utres soures de )ututions telles que les )ututions de l9étt initilD ou ien les )ututions dûes u proessus sttistique d9hdronistionF hns le ontexte du progrmme fiD l ollortion e réemment pulié le résultt des mesures de @oAvrines de distriutions nettes de pionsD kons et protons à pseudorpidité entrle @∆η < 0.5A et à s p T @0.4 < p T < 1.6 qeAD dns des olliE sions euEeu à √ s N N = 7.7D IIFSD IRFSD IWFTD PUD QWD TPFR et PHH qe PIIF hns ette pulitionD les @oAvrines sont notmment étudiées en fontion de l entrlité des ollisions @représentée pr l nomre de nuléons prtiipnts ⟨N part ⟩AD omme montré dns l (gure PFWF ges vrines et ovrines sont utilisées pour onstruire des rtios de proxies omprles ux rtio de suseptiilitésD exprimés dns l9éqution @PFQFIVAF sls sont étudiés en fontion leur dépendene à l entrlité et à l9énergie de ollisionD omme montré dns l (gure PFIHD (n de herher un quelonque signe de ritilitéF rllèlement à elD les uteurs de PQR ont mené une étude sur l déomposition des ontriutions de di'érentes espèes hdroniques ux suseptiilités totlesF sls ont pour el utilisé le gz de résonnes de hdrons @qrAD un modèle sttistique dns lequel un gz de hdrons intérgissnt dns leur étt fondmentl est représenté pr un un gz de hdrons et leurs résonnes sns intertionsF in omprnt ensuite dns quelle proporE tion hque espèe hdronique ontriue ux suseptiilités totles otenues pr luls de gh sur réseu @voir (gure PFIIAD ils ont pu proposer des nouveux proxies pour les rtios C QS = χ QS 11 /χ S 2 et C BS = χ BS 11 /χ S 2 D lterntifs à eux utilisés pr l ollortion eF ges proxies lterntifs sont expliités dns les équtions @PFQFPSA et @PFQFPTAD et furent séletionnés à prtir de leur proximité ux rtios exts de suseptiilités tels que présenté dns l (gure PFIPF IQW eixhs iF ÉwÉ pexÇes hi ve rÈi fsé sur les résultts des deux pulitions itées préédemmentD l9idée priniple de mon étude est lors d9utiliser le générteur d9événements @qiA iy (n de omprer les proxies mesurés pr e ve les proxies lterntifs résultnts de l9étude menée ve le modèle du qrF iy est un qi dit 4générique4D dns le sens où il permet de générer di'érents types de ollisions dns leur intégrlitéD qu9il s9gisse d9nnihiltion e + Ee -D ou ien de ollisions pEp D pEA ou AEA F eynt été vnt tout développé pour l9étude de ollisions hdroniquesD iy repose sur une struture modulire lssique de générteurs d9événements dédiés ux gsvF outes les étpes y sont simulées suessiveE ment dns un ordre hronologiqueD omme illustré sur l (gure QFIF ne des priniples rtéristiques distintive et unique d9iy réside en l fE qD utilisée pour générer les onditions initiles des ollisions hdroniquesF ille résulte de l9union du modèle des prtonsD utilisé pour luler des proessus inlusifs dits durs @où Q 2 > 1 qeAD ve l théorie de qriovEegge @qAD une théorie d9intertions prtoniques mutliples sée sur le formlisme de l mtrie de di'usion SF hns e modèleD les intertions entre les prtons qui onstituent les projetiles sont représentées pr des ojets mthémtiques ppelés omeronsF ges ojets représentent physiquement des éhelles de prtonsD et peuvent voir di'érentes strutures possiles @représentées shémtiquement dns l (gure QFRA selon l nture et l9énergie des prtons à leurs exE trémitésF ges rtéristiques déterminent lors le formlisme employé pour simuler l9évolution de l sde prtoniqueD (n de luler les setions e0es qui sont lors ftorisées omme expliité dns l9éqution @QFQFVAF ves e'ets nonElinéires dus à l stE urtion des gluonsD dont l fréquene ugmente à hute énergieD sont pris en ompte vi une éhelle de sturtion individuelle pour hque omeronF ghque omeron est soit entierD ontriunt lors ve un terme d9interférene dns le lul de setion e0e toE tle d9intertionD ou soit oupé et prtiipe lors à l prodution de prtiule @voir (gure QFSAF ne fois généréesD les distriutions de prtons sont lors modélisées pr des ordesD des hînes de gluons ynt pour déut et (n une pire qEq @qEgEFFFEgEqAD qui possèdent une tension égle à ∼ 1 qeGfm et se frgmentent pr rétion de pires de @diAqurks qEq GqqEq qF ges ordesD priniplement longitudinles et dont l dimension trnsverse est usée pr des 4kinks4 de gluonsD évoluent lors suivnt l dynmique d9un lgrngE ien invrint de vorentzF hns le s de ollisions impliqunt de nomreux éhnges de omeronsD tel que les ollisions AEA ou ien même ertines ollisions pEp de hute multipliitéD l densité de ordes devient tellement importnte qu9elles ne peuvent lors plus frgmenter indépendemment les unes des utresD omme représenté dns l (gure QFWF hns e sD le système est sépré en deux prties distintesD dns une proédure pE pelée core-coronaF hns l coronaD région moins denseD les segments de ordes ynt une impulsion trnsverse su0snte pour éhpper u core évoluent suivnt l proédure stnE drd dérite préédemmentF v9évolution du coreD l région de hute densité d9énergieD est simulée à l9ide d9équtions d9hydrodynmique reltiviste visqueuseD (n de reproduire le omportement )uidique du qF our elD il est possile de hoisir entre deux équtions d9étt di'érentes X dns ette étudeD les simultions rélisées utilisent une éqution d9étt ontennt uniquement un crossover entre l phse hdronique et le qF vorsque l denE sité d9énergie repsse sous une vleur ritiqueD hque ellule est lors hdronisée selon un proessus mirononique d9près une densité de proilité dérite dns l9éqution @QFRFUAF ne fois le système omplètement hdroniséD les réEintertions entre prtiules formées sont simulées à l9ide du modèle de trnsport mirosopique rwhF gette phse hdronique utrement ppelé 4sde hdronique4D 'ete à l fois l himie du sytème mis ussi l distriution inémtique des prtiulesD et joue un rôle importnt dns l9étude des umulnts présentée en setion iFRF IRH iFPF wysesyx i yftigsp hi ve rÈi E.2 Motivations et objectifs de la thèse uivnt le développement d9iy R durnt les quelques dernières nnéesD un des ojetifs de m thèse étit d9ider à l préprtion de s di'usion puliqueF gel requiert en prtiuler de s9ssurer que l prmétristion de l9ensemle des éléments du qi permet de reproduire orretement l prodution de prtiules pour un mximum de systèmes et d9énergies di'érentesD (n d9évluer ses limites d9pplitionF v question de l gestion des données et de leur nlyse revêt notmment un spet importnt pour le développeur dns e proessus de vlidtionD utnt que pour les potentiels futurs utilisteurs d9iyF 9il possède déjà un système d9nlyse d9événements 4à l volée4 qui lui est propreD et qui permet de reproduire l pluprt des nlyses expérimentlesD il ne s9git ps d9un outil stndrdiséF einsiD une de mes tâhes onsiste à développer un interfe entre iy et l9outil d9nlyses et de omprison ivetF gel implique d9jouter un nouveu formt d9enregistrement des données d9événements simulés dns un premier tempsD puis de développer l9rhiteture néessire pour pouvoir fire ppel à ivet systémtiqueE ment lors de l9utilistion d9iyF ge trvil s9ompgne de l rédtion d9une doumenttion ssoiéeD tnt pour l9utilisteur que pour les développeursD vi des notes internesF eprès une présenttion rpide de ivetD le développement de ette nouvelle interE fe ser insi résumé en setion iFQF eve omme visée (nle le proessus de vlidtion d9iy RD le premier ojetif est d9utiliser ette nouvelle interfe (n d9employer ivet pour omprer les résultts de simultions otenues ve iyD ux résultts expérimenE tux de ollisions euEeu ux énergies du progrmme fiF gependntD peu d9nlyses sont tuellement disponiles dns ivet à es énergiesF r onséquentD je suis hrgé de réolter des données expérimentlesD insi que d9érire les nlyses orrespondntes dns le système d9nlyse 4à l volée4 d9iyD (n de pouvoir proéder à l vlidtion d9iy R pour les gsv ux énergies du progrmme fiF einsiD le déut de l setion iFR porter sur les résultts distriutions en pseudorE pidité η et les spetres en p T de prtiulesF ves ollisions euEeu simulées à ette osion pourront lors être utilisées (n de réliser l9étude des proxies de umulnts des hrges BD Q et SD introduite à l (n de l setion iFIF won premier ojetif à e sujet est de reproduire l9nlyse rélisée pr l9expériene e sur l mesure des @oAvrines de distriutions nettes de π ± D K ± et p(p)D près une rpide étude de l9e'et de lrgeur de ins en entrlité sur es @oAvrines lorsque mesurées en fontion de l entrlitéF e(n de omler le fossé entre les études théoriques menées sur les umulnts de hrges onservéesD et le proxies mesurés expérimentlementD je prévois ensuite de mesurer dditionnellement les @oAvrines des multipliités nettes de ΛD Ξ -et Ω -D (n de pouE voir onstruire les nouveux proxies lterntifsF IRI eixhs iF ÉwÉ pexÇes hi ve rÈi hns un seond tempsD l9idée est de onfronter à l fois les proxies utilisés pr e insi que es proxies lterntifsD ux rtios de @oAvrines de hrges BD Q et S ellesEmêmesD tous mesurés à prtir de simultions rélisées ve iyF v9ojetif étnt lors d9évluer à quel point les proxies lterntifs et eux utilisés pr e di'èrent les uns des utresD et notmment de regrder leurs évolutions respetives en fontion de l9énergie de olllisionF gel permettr insi de véri(er si les proxies lterntifs sont e'etivement plus e0es pour reproduire les umulnts de hrges onservées que les proxies utilisés pr eF uisqu9un qi permet d9voir ès à l liste omplète des prtiules réées lors d9une ollision simuléeD il est possile de omprer es proxies ux réels umulnts des hrges BD Q et S orrespondntesD en utilisnt toutes les prtiules issues de l simultion porE tnt es hrgesF he plusD l onstrution modulire d9iy permet d9voir ès ux distriutions de prtiules vnt les sdes hdroniquesD et don d9étudier à quel point l phse hdronique modi(e le signl des umulnts de multipliités nettes de prtiulesF v suite de l9étude onsiste don à qunti(er l9impt des sdes hdroniques sur les @oAvrines de hrges onservées et leurs proxiesD en mesurnt es derniers vnt et près l phse hdronique simulée à l9ide d9rwhF in(nD l proédure de core-corona utilisée dns les simultions d9iy permet de distinguer si les prtiules produites proviennent ou non du coreD qui est ensé représenter le q réé dns les gsvF sl est don possile d9estimerD pour les @oAvrines de distriutions de prtiulesD quelle proportion du signl trouve son origine dns le coreD et porte don e'etivement l tre de potentielles )ututions ritiquesF v version d9iy utilisée pour ette étude est iy QFRSID une version beta d9iy R Y tous les résultts physiques présentés en setion iFR sont don otenus à prtir de simultions rélisées ve ette versionF À noter que l9ojetif de e trvil n9est ps d9étudier le signl du point ritique en tnt que telD mis ien de se onentrer sur les oservles expérimentles utilisées pour le sonderF in prtiulierD l9ojetif est de déterminer à quel point les proxies utilisés sont (dèles ux rtios de umulnts de hrges nettes onservées orrespondntesF sl urit été possile d9employerD dns les simultions d9événements utiliséesD l deuxième éqution d9étt disponile pour l9évolution du core dns iy RD ontennt une trnsition de 1 er ordre et un g en plus du crossoverF gependntD le formlisme utilisé pour simuler l9évolution hydrodynmique du core ne permet ps l propgtion de )ututions thermles telles que elles générées pr des phénomènes ritiquesF ge sujet fit tuellement l9ojet de reherhes tivesD et ien que ertines pprohes permettrient depuis peu de le fireD elles n9ont ps enore été implémentées dns iyF ve leteur doit don grder à l9esprit que les résultts montrés iEprès n9exhient en uun s des omportements dus à une quelonque ritilité du digrmme de phse de l mtière nuléireF IRP iFQF hÉivyiwix igrxsi y iy R E.3 Développements techniques pour EPOS 4 gomme expliqué préédemmentD le proessus de vlidtion d9un qi est une étpe ruile (n de (xer tous les prmètres physiques des di'érents modèles sousEjentsF ge proessus néessitnt ependnt un trvil long et fstidieux d9nlyse de données simulées et de omprison ux résultts expérimentuxD il est vntgeux de pouvoir systémtiser ette étpe utnt que possileF yrD l9outil ivet justement été développé dns e utF sl s9git d9un ode omposé d9un ensemle de liririesD ontennt de très nomreuses nlyses reensées pr pulitionsD et dont l philosophie est d9o'rir un outil utomtiqueD stndrdisé et file à prendre en min pour omprer les données expériE mentles ux résultts de simultions de qiF fien qu9à l9origine priniplement utilisé pour l9étude de l physique du w et des fontions de distriutions prtoniques dns les ollisions e + Ee -et pEp D ivet onnu de nomreuses méliortions es dernières nnées (n de filiter l9utilistion d9nlyses dédiées ux gsvF our ette risonD il est ppru nturel de vouloir ssoier ivet à iy R (n d9ssister dns le proessus de vlidtionF he plusD ve en vue l9ojetif d9une di'usion pulique d9iy RD il est primordil d9o'rir une omptiilité ussi lrge que possile ux di'érents outils utiles à l9utilisteurD et ivet remplit églement e ritère de pr s filité d9utilistionF hns ivetD hque nlyse onsiste en un ensemle de qutre (hiers X un (hier gCC dns lequel est odée l9nlyse orrespondnte à l pulition ssoiéeD un (hier u formt ODA ontennt les données expérimentles à omprerD un (hier ontennt les informtions générles sur l9nlyseD et un (hier ontennt les détils sur l90hge des grphesF in e'etD ODA est un ensemle de liriries dédié à l90hge des donnéesD en plus d9être un formt stndrd dns lequel les données expérimentles disponiles en lire ès peuvent être téléhrgéesF v filité d9utilistion de ivet réside dns le fit qu9il ne su0t que de quelques lignes de ommnde pour l9exéuterF sl su0t d9voir à disposition un (hier u formt repMCD un formt stndrd pour stoker les informE tions de ollisions simuléesD et une seule ligne de ommnde permet d9exéuter l9nlyse de son hoix sur les événements stokés dns e (hierF in sortieD un (hier ontennt les résultts d9nlyse u formt ODA églement est rééF ves résultts d9nlyse y sont ordonnés de l même mnière que dns le (hier ODA ontennt les données expérimenE tles de référeneF he ette fçonD une seule utre ligne de ommnde est su0snte pour générer les grphes des omprisons entre données expérimentles et résultts d9nlyse sur les événements simulésF in(nD dns le dre d9nlyses de gsvD il est néessire de rjouter une étpe pour lirer l entrlité des événements vnt d9utiliser l pluprt des nlyses dédiéesF sl fut en e'et dns e s ppliquer une nlyse de lirtion en entrlité dns un premier tempsD (n de générer une première distriution qui sert de référene pour dé(nir les di'érentes lsses en entrlitéF gette distriution ser lors utilisée omme prérequis pour n9importe quelle nlyse néessitnt une telle lirtionD qui sur lors dns quelle lsse en entrlité pler hque événement nlyséF ges ommndes sont expliitées dns l sousEsetion RFIFIF v première étpe (n d9dpter iy à l9utilistion de ivet est ien sûr d9jouter l possiilité d9enregistrer les événements simulés u formt repMCD qui est le seul forE mt lu pr ivetD e qui est dérit dns l sousEsetion RFQFIF our elD je suis reprti du trvil entmé pr wri tefnikD en omplétnt tout d9ord les informtions physiques qui sont enregistrées u formt repMC pour hque événementF t9i notmE ment jouté les informtions onernnt l setion e0e d9intertionD le nomre de nuléons prtiipnts à l ollision N part D le nomre de nuléons spetteurs N spec F elors qu9il n9étit initilement ps possile d9enregistrer que les prtiules dns l9étt (nlD j9i rjouté l possiilité d9enregistrer les désintégrtions files dns hque événementF IRQ eixhs iF ÉwÉ pexÇes hi ve rÈi gel permet de orriger de l ontmintion pr les désintégrtion files lors d9nlyses de spetres exlusifsD qui ne onsidèrent que les prtiules primires d9une ertine esE pèe hdroniqueF n exemple de sde de désintégrtions files enregistrée u formt repMC est illustré en (gure RFUF t9i églement modi(é l mnière de luler l9énergie des prtiules pour le formt repMC à prtir des informtions fournies pr iyD (n de résoudre des prolèmes de préision numérique mennt à des résultts physiquement inorrets @notmment des prtiules ve une vleur d9impulsion supérieure à leur énE ergieAF v formule désormis utilisée est expliitée dns l9éqution @RFQFRAF t9i rjouté l possiilité d9ppliquer une trnsltion en rpidité u référentiel de l ollision simuléeD suivnt l trnsformtion donnée dns l9éqution @RFQFSAD puisque les ollisions sont touE jours simulées dns le référentiel du entre de msse pr iyF yrD expérimentlementD les référentiels du entre de msse et du lortoire pour les systèmes symétriques tels que les ollisions pEA ne ps onfondusD et les nlyses ivet sont lors dé(nies dns le référentiel du lortoireF gette fontion permet don de s9ssurer que les oordonnées des prtiules enregistrées u formt repMC sont ien dé(nies dns le on référenE tielF sl (nlement été néessire de modi(er le ode d9iy (n de donner le hoix à l9utilisteur de générer ou non les (hiers ontennt l9enregistrement de ollisions simulées u formt repMCD insi que l possiilité d9jouter ou non une trnsltion en rpidité u système simulé omme dérit préédemmentF iy étnt désormis omptile ve ivetD l deuxième prtie du trvil lors onsisté à intégrer l9utilistion de ivet dns le système d9nlyse 4à l volée4 d9iyF ge système nlyse hque événement un à un près leur simultionD (n de ne grder que le résultt des nlyses de es simultions sns voir néessirement esoin d9enregistrer et stoker les événements en questionF in l9éttD un utilisteur urit esoin d9exéuter iy dns un premier temps (n de générer un (hier u formt repMC ontennt les listes de prtiules des événements simulésD pour ensuite devoir exéuter ivet dns un seond tempsD utnt de fois que le nomre d9nlyses qu9il souhiterit ppliquer sur es événementsF v9idée d9intégrer ivet u système d9nlyse d9iy permettrit lors de réduire le nomre d9étpes intermédiires et don de simpli(er le proessus de ompriE son entre les simultions d9iy et les données expérimentles disponiles dns ivetF he plusD el permettrit d9éonomiser de l9espeEdisqueD puisqu9il ne serit lors plus néessire de stoker tous les événements que l9utilisteur souhite nlyser u formt repMCD mis uniquement ertins événements de mnière temporireD les uns près les utresF ve proessusD résumé de mnière shémtique dns l (gure RFIHD onsiste à trnsmetE tre dns un premier temps à un sript ython développé pour l9osion les instrutions dé(nies dns un (hier d9options lssique d9iyD vi un (her temporire d9extension 4.dataR4F ve sript lit lors l liste des nlyses requises pr l9utilisteurF ne fois que le (hier repMC ontennt l9enregistrement des ollisions simulées est produitD ivet est suessivement exéuté pour hune des nlyses requisesF ve (hier ODA onE tennt les résultts d9nlyse otenu est lors lu pr le sript ython puis suppriméD pour trnsrire les résultts dns le formt utilisé pr le système d9nlyse d9iy @4.histo4AD (n de entrliser tous les résultts d9nlyses @otenus vi ivet ou ien diretement iyAF v rison pour el est que le nomre d9nlyses disponiles dns ivet vrie d9une expériene à une utreD et repose sur l onne volonté de ollortions de soumetE tre leurs nlyses à ivetF einsiD dns de nomreux sD et notmment pour les ollisions euEeu ux énergies du progrmme fiD le nomre d9nlyses disponiles vi ivet est insu0snt pour le proessus de vlidtion d9iy RD et néessite d9utiliser simultnéE ment le système d9nlyse d9iy pour ompléterF IRR iFRF Éve v9Éhi hi gwvex hi greqi gyxiÉi ve s des nlyses de gsv rjoute à e fontionnement quelques sutilitésF re qu9il est néessire de posséder une distriution en entrlité sur l9ensemle des événements nlysés u prélleD il n9est ps possile d9exéuter l lirtion sur un sousEensemle d9événements pour utiliser el omme référene pour les nlyses suivntesF einsiD les résultts de es nlyses de lirtion sont stokés dns le répertoire du ode d9iyF einsiD à hque fois qu9une nlyse ivet néessitnt une lirtion en entrlité est ppeléeD elle utilise omme référene une distriution en entrlité otenue préllement sur un très grnd nomre d9événementsF gel permet de s9ssurer que le reltivement petit nomre d9événements nlysés à hque simultion soit orretement lssi(é en terme de entrlitéF sl est insi possile de trouverD en (gure RFWD un extrit de (hier d9option d9iyF sont expliitées les ommndes utilisées (n d9tiver l prodution de (hier u forE mt repMCD d9ppliquer une trnsltion en rpidité u référentiel du système simuléD et d9ppeler ivet (n d9nlyser les événements simulésF fien que e système soit opértionnelD il n9est ps prfit et est toujours sujet à de potentielles méliortionsF v première onsisterit à exéuter ivet en utilisnt un système de leture de données de type pspyD qui permettrit de ne même plus voir à enregistrer des (hiers tempoE rires u formt repMC mis de lire les événements un à un sns les grder une fois l leture e'etuéeD réduisnt enore l9espe disque utilisé dns le proessusF ve fit de lisser à l9utilisteur l possiilité de onserver les (hiers ODA d9nlyse otenu pr l9exéution de ivet permettrit églement de ne ps reposer sur le système d90hge des grphes propre à iyD mis de pouvoir utiliser les lirires ODA développées à et e'etF E.4 Résultats sur l'étude des cumulants de charges conservées ne fois l9rhiteture d9nlyse néessire u proessus de vlidtion développéeD il est lors possile de réliser une omprison systémtique des résultts de simultions d9iy QFRSI ux données expérimentlesD et insi de réliser l9étude sur les umulnts motivée préédemmentF te rppelle que je me suis ii intéressé ux ollisions euEeu dns un domine en énergie de ollision de 7.7 ≤ √ s N N ≤ 200 qe du progrmme fiF re que les simultions d9iy sont oûteuses en temps de lulD à use de l9évolution hydrodynmique du core en prtiulierD et qu9il est néessire de simuler des ollisions à de nomreuses énergiesD le nomre d9événements disponile à hque énergie est reltivement limitéD omme illustré dns le tleu SFIF ves énergies de ollisions uxquelles j9i hoisi de omprer les simultions ux données expérimentles iEprès dépendentD vnt toutD de l disponiilité de données expérimentlesF eussiD pour des risons de lisiilité des résulttsD je n9i prfois séletionné que ertines de toutes les énergies de ollisions disponilesD tout en grdnt à l9esprit de snner u plus lrge posE sile en terme de vleurs d9énergieF v prodution de prtiules à toutes les énergies simulées été omprée ux résultts expérimentuxD en portnt un intérêt prtiulier à l région inémtique des prtiules utilisées pour onstruire les umulntsD i.e. |η| < 0.5 et 0 < p T < 2 qeF our omE menerD les distriutions en pseudorpidité de prtiules hrgées ont été omprées ux données expérimentles à IWFTD TPFR et PHH qeGeD telles que montrées dns l (gure SFIF siD iy se révèle être ple de reproduire orretement es distriutions exepté à IWFT qeGe pour les ollisions les plus entrlesF ges résultts sont ependnt très lrgeE IRS eixhs iF ÉwÉ pexÇes hi ve rÈi ment stisfisnts dns l9ensemleF ves spetres en p T on ensuite été étudiés pour les hdrons légers @π ± D K ± et p / pAD illustrés dns les (gures SFPD SFQ et eFI à eFTD insi que pour les ryons étrnges @Λ/ ΛD Ξ -/ Ξ+ et Ω -/ Ω+ AAD présentés dns les (gures SFR à SFT et eFUF ges (gures montrent insi que les spetres p T otenus à prtir des événements simulés ve iy QFRSI sont en très on ord ve les données expérimentles ux énergies de ollision supérieures à PH qeGeD puis s9en értent de plus en plus à mesure que l9énergie de ollision déroît sous √ s N N ≈ 20 qeGeF ves résultts otenus pour l prodution de prtiules dns l9intervlle inémE tique d9intérêt pour l9étude des umulnts montre qu9iy QFRSI otient des résulE tts en on ord quntittif ve les données expérimentlesD u moins uEdessus de √ s N N ∼ 20 qeF euEdessous de ette vleurD les résultts de simultions divergent peu à peu des données expérimentles à mesure que l9énergie de ollision déroîtD ien qu9en onservnt une llure enore reltivement proheF yn onstte notmE ment un douissement progressif des spetres en p T D 9estEàEdire une modi(tion des spetres ve une prodution trop importnte dns les plus sses vleurs de p T D et ps ssez importnte à plus hut p T D ompré ux données expérimentlesF ges résultts ne sont ps inttendusD puisqu9une des hypothèses importntes de l fqD utilisée pour simuler les onditions initiles dns iyD est que toutes les inE tertions doivent voir lieu simultnémentF yrD à plus sse énergieD l ontrtion de vorentz dns l diretion longitudinle des noyux ollisionnnts est moins importnteD et es noyux vont lors mettre plus de temps à se trverserF einsiD de rpides luls permettent d9estimer qu9uEdessous d9une énergie de ollision d9environ une vingtine de qeGeD l9épisseur de es noyux entrînerit un temps d9intertion su0smment long pour que les prtons du projetile ient le temps de réintérgir ve eux de l ileF hns e sEiD l fq employée dns iy n9o'ririt lors plus un formlisme dpté pour étudier e genre de ollisionsF gependntD es luls n9étnt qu9pproximtifsD puisque reposnt sur une hypothèse purement qulittive qunt à l9épisseur néessire pour perE mettre plusieurs intertions suessives entre prtonsD il est di0ile d9en tirer une vleur d9énergie de ollision limite strite pour pouvoir utiliser iyF e(n de luler les @oAvrines de distriutions nettes de π ± D K ± et p(p) dns les simultions d9iy QFRSID j9i reproduit l9nlyse e'etuée pr l9expériene eF te me suis pour el servi du système d9nlyse d9iyD et i don dû développer les routines d9nlyse néessiresF te les i développées en donnnt l possiilité de luler les umulnts d9ordre I à RD pour les hrges onservées BD Q et S insi que les distriutions nettes de π

± D K ± D p(p)D Λ(Λ)D Ξ -(Ξ + ) et Ω -(Ω +
) vnt ou près les sdes hdroniquesF t9y i de plus jouté l possiilité de orriger es distriutions des ontriutions dues ux désintégrtions filesD pour le s d9espèes hdroniques identi(éesF hns le s de hrges onservéesD le lul se fit systémtiquement à prtir des prtiules primordilesD puisque l9étrngeté S n9est ps onservée pr l9intertion fileF in(nD es routines ont été développées de mnière à être filement étendues à d9utres espèes de prtiulesD ou ien même à des ordres de umulnts supérieursF ves détils onernnt le fontionnement et l9intégrtion de ette nlyse sont donnés dns l9nnexe gF IRT iFRF Éve v9Éhi hi gwvex hi greqi gyxiÉi ves résultts de @oAvrines des distriutions de π ± D K ± et p(p)D représentées en fontion de N part D sont exposés dns les (gures SFU et SFVF yn onstte que les résultts d9iy sont en ord à l fois qulittifD mis ussi quntittif dns l9ensemleD ve les données de eF gel est vri pour des énergies de ollisions supérieures à ∼ 20 qeGe en prtiulierD lors que es résultts présentent des divergenes de plus en plus importntes ve les données expérimentles ve l déroissne de l9énergie de ollisionD re)étnt les di0ultés d9iy à reproduire orretement les distriutions de prtiules à es énergiesF ves rtios de proxies formés pr es @oAvrinesD exposés dns l (gure SFWD exhient lors logiquement le même omportement visEàEvis des résultts expérimentuxF euune lire dépendne à l entrlité n9est oservée dns les )ututions sttistiquesD qui sont ssez importntes à use du nomre reltivement file d9événements simulés pour hque énergieF v9étpe suivnte de l9étude onsiste lors à omprer les résultts de proxies de e ux proxies lterntifs CQS et CBS / C′ BS expliités dns les équtions @PFQFPSA et @PFQFPTAD respetivementF euun proxy n9ynt été proposé pour le rtio C BQ = χ QB 11 /χ B 2 D je me suis inspiré de l9étude sée sur le modèle du qr pour proposer un proxy lterntif CQB expliité dns l9éqution @SFPFRAF te me suis pour el sé sur l déomposition des ontriutions hdroniques ux suseptiilités χ QB 11 et χ B 2 D présentée dns l (gure SFIHD en utilisnt les mêmes rguments que les uteurs (n de onstruire e rtioF ve résultt des omprisons entre rtios de @oAvrines de hrges onservéesD et de leurs di'érents proxies ssoiésD est présenté dns l (gure SFII pour S di'érentes énergiesD en fontion de l entrlité de l ollisionF ves mêmes résultts sont présentés en fontion de l9énergie de ollision dns l (gure SFIP pour les ollisions les plus entrles et les plus périphériquesF hns les deux sD les résultts expérimentux de e sont uniquement montrés à titre inditifD pour omprer ux résultts de proxies orrespondnts ve iy QFRSIF ves proxies lterntifs CQS D CBS et CQB @en leuA se révèlent être de ien meilleurs proxies des rtios de @oAvrines de hrges onservées @en vertA que les proxies de e @en rougeAF yn oserve en e'et qu9ils se situent toujours très prohes quntittivement des rtios de hrges orrespondntsD là où les proxies de e en sont plus éloignésD u dessus de √ s N N ≈ 20 qeGeF euEdessous de ette énergieD les di0ultés d9iy QFRSI à reproduire orretement l prodution de prtiules rendent non pertinente toute interpréttion du omportement de es rtiosF einsiD dns l reherhe d9un potentiel g du digrmme de phse de l mtière nuléireD les quntités suivnt sont de meilleurs proxies que eux utilisés jusqueElà pr l ollortion eX

CQS = 1 2 . σ 2 K σ 2 K + σ 2 Λ , CBS = σ 2 Λ σ 2 K + σ 2 Λ , CQB = σ 11 πp + σ 2 p 2σ 2 p + σ 2 Λ
sl est intéressnt de noter que l9utilistion presque exlusive de vrinesD insi que le seul jout de l vrine de distriution nette de Λ en plus des @oAvrines déjà mesurées pr eD sont su0snts pour onstruire des proxies quntittivement plus prohes des rtios de umulnts de hrges onservéesF IRU eixhs iF ÉwÉ pexÇes hi ve rÈi ro(tnt de l onstrution modulire d9iyD j9i ensuite pu mesurer l9impt des sdes hdroniques sur les @oAvrines de hrges et de distriutions de prtiulesD insi que des rtios et proxies orrespondntsF our elD j9i ompré l vleur de es oservles lulées à prtir des prtiules otenues juste près hdronistionD ve leur vleur lulée à prtir des prtiules à l (n de l9évolution de l ollisionF ves résultts montrent que les vrines et ovrines de distriutions nettes de prtiulesD montrées respetivement dns les (gures SFIQ et SFIRD sont très fortement imptées pr l phse hdroniqueD ontrirement ux @oAvrines de hrges onservées exposés dns les (gures hFI et hFPF einsiD l9mplitude du signl est générlement multipliée pr un fteur P à Q durnt ette phseD priniplement à use des désintégrtions de résonnes et rétions inélstiques suessives y ynt lieuF gependntD les rtios otenus à prtir de es @oAvrines sont qunt à eux très peu modi(ésF CQS et CQB s9vèrent insi être de très ons proxies des rtios de umulnts de hrges onservées orrespondntsD puisque leur mplitude n9est que très peu modi(ée pr l phse hdroniqueD omme qunti(é dns l (gure SFITF einsiD l9mplitude d9un potentiel signl ritique porté pr es oservles survivrit ux sdes hdroniques et pourrit être mesurée expérimentlementD re)étnt lors de mnière (dèle le signl produit près hdronistion du systèmeF eul CBS forme un proxy peu dptéD dns le sens où son mplitude est modi(ée d9un fteur P pr l phse hdroniqueD et ne re)ète don ps à l (n de l ollision le signl otenu près hdronistionF v dernière étpe de mon étude onsisté à luler quelle proportion des rtios de umulnts de hrges onservéesD et des proxies lterntifs ssoiésD provient e'etiveE ment du coreD orrespondnt à l9imge physique du q dns les simultions d9iy QFRSIF ves résulttsD montrés dns l (gure SFIUD indiquent que l9intensité du signl des umulnts de hrges onservées et de leurs proxies provient qusi exlusivement du 4ore4 pour les prtiules onsidérées dns ette nlyseD dns les ollisions d9énergie supérieure à IH qevGeF einsi les )ututions de distriutions de prtiules mesurées près hdronisE tionD re)etées de mnière reltivement (dèle à l (n de l ollision omme monE tré préédemmentD sont portées presque exlusivement pr des prtiules issues de l9hdronistion du 4ore4D pour des prtiules onsidérées ve |η| < 0.5 et 0 < p T < 2 qeF euEdessous de √ s N N D ette proportion diminueD simplement dû u fit que l proportion du 4ore4 est moins importnte pour les systèmes de sse énergieF in onlusionD ette étude pporte des résultts très importnts en terme d9oservles expérimentles employées pour sonder l présene d9un signlD dû à un potentiel gD dns le digrmme de phse de l mtière nuléireF ne poursuite de e trvil pourrit noE tmment onsister à herher un potentiel proxy lterntif pour C BS qui survivrit ux sdes hdroniques sns voir l9mplitude de son signl modi(éF gette étude pourE rit églement être étendue ux umulnts d9ordre supérieursD d9utnt plus intéressnts qu9ils sont plus sensiles à l ritilitéD et don lrgement étudiés ujourd9huiF

IRF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F IQ IFP sllustrtion of the J = 0 nd J = 1/2 otets s representtions of the (3) groupF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F
ollisionsF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F UR
RFS ixmple of n nlysis de(ned in .optns (le to get p T distriution of

π + F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F US RFT ixmple of the ontent of repMC (le for E ollision t PFUT qeGeF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F
UV RFU ixmple of the reord of dey hin of prtile in repMC (le for E ollision t PFUT qeGeD from the sme event displyed in (gure RFTF xote tht the preision on numeril vlues hve een trunted for the purpose of the (gureF

F F F F F F F F F F F F F F F F F F F F F F F F F F F VP
RFV ixmple of n nlysis de(ned in .optns (le to get p T distriution of for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4}A @dt from QIHAF F F F F F F F F F F F F F F WR SFQ rnsverse momentum spetr of π ± D K ± nd p/p t y = 0.8D for di'erent entrlity lsses in euEeu events t √ s N N = 62.4 qeF petr for the most entrl events re t rel sleD while the others re sled y ftors 10 -1 @ISEQH7A nd 10 -2 @QHESH7A @dt from QIIAF F F F F F F F F F F F F WS SFR rnsverse momentum spetr of ΛD ΛD Ξ -D Ξ + nd Ω -+ Ω + for di'erent entrlity lsses in euEeu events t √ s N N = 200 qeF petr for the most entrl events re t rel sleD while the others re sled y ftors 10

π + F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F VR
-x @x = {1, 2, 3, 4}A @dt from QIQAF F F F F F F F F F F F F F F F F F F F WT SFS rnsverse momentum spetr of ΛD ΛD Ξ -D Ξ + D Ω -nd Ω + for di'erent
entrlity lsses in euEeu events t √ s N N = 27 qeF petr for the most entrl events re t rel sleD while the others re sled y ftors 10 for entrl @leftA nd peripherl ollisions @rightAF F F F F F F F F F F F F F F IIH eFI rnsverse momentum spetr of respetively line y line π + D π -D K + nd K -D t |y| < 0.1D for entrlity lsses from H7 to RH7 @leftA nd RH7 to VH7 @rightA in euEeu events t √ s N N = 27 qeF sn eh plotD spetr for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4}A @dt from IUUAF F F F F F F F F F F F F F F IIV eFP me thn previous (gure ut for p nd pF F F F F F F F F F F F F F F F F F IIW eFQ rnsverse momentum spetr of respetively line y line π + D π -D K + nd K -D t |y| < 0.1D for entrlity lsses from H7 to RH7 @leftA nd RH7 to VH7 @rightA in euEeu events t √ s N N = 14.5 qeF sn eh plotD spetr for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4}A @dt from IUUAF F F F F F F F F F F F F F F IPH eFR me thn previous (gure ut for p nd pF F F F F F F F F F F F F F F F F F IPI eFS rnsverse momentum spetr of respetively line y line π + D π -D K + nd K -D t |y| < 0.1D for entrlity lsses from H7 to RH7 @leftA nd RH7 to VH7 @rightA in euEeu events t √ s N N = 7.7 qeF sn eh plotD spetr for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4}A @dt from IUUAF F

-x @x = {1, 2, 3, 4, 5, 6}A @dt from QISAF F F F F F F F F F F F F F F F F WU SFT rnsverse momentum spetr of ΛD ΛD Ξ -D Ξ + D Ω -nd Ω + for di'erent

Introduction 7 1

 7 Particle physics: from theory to experiments 11 IFI he tndrd wodel of prtile physis F F F F F F F F F F F F F F F F F F F IQ IFIFI qenerl desription F F F F F F F F F F F F F F F F F F F F F F F F F F F IQ IFIFP vimittions of the tndrd wodel F F F F F F F F F F F F F F F F F F IR IFIFQ feyond the tndrd wodel F F F F F F F F F F F F F F F F F F F F F F IT IFP rdroni physis nd untum ghromohynmis F F F F F F F F F F F F F IT IFPFI he foundtion of gh F F F F F F F F F F F F F F F F F F F F F F F F IU IFPFP row to del with ghX methods 8 phenomenologil pprohes F PH 2 The hottest matter of the Universe 21 PFI yn theoretil levelX from (rst preditions to urrent models F F F F F F F PP PFIFI he theoretil genesis ehind the disovery of the q F F F F F F PP PFIFP he phse digrm of nuler mtter F F F F F F F F F F F F F F F F F PS PFP tudying the q t the experimentl level F F F F F F F F F F F F F F F F F PU PFPFI uinemtis of highEenergy ollisions F F F F F F F F F F F F F F F F F PU PFPFP he experimentl pprtus F F F F F F F F F F F F F F F F F F F F F F PW PFPFQ wethods to study the q F F F F F F F F F F F F F F F F F F F F F F QP PFQ pous onX ritility in the nuler phse digrm F F F F F F F F F F F F F F QR PFQFI hermodynmi suseptiilities nd netEhrge umulnts F F F F F QS PFQFP vimits nd shortomings of experimentl nd theoretil oservlesF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F FQW PFQFQ e results 8 enhned proxies for 2 nd order umulnts F F FF F RI 3 The EPOS event generator 47QFI qenerlities on event genertors F F F F F F F F F F F F F F F F F F F F F F F F RV QFIFI ivent genertors 8 highEenergy physis F F F F F F F F F F F F F F F RV QFIFP ivent genertors for hevyEion ollisions F F F F F F F F F F F F F F F RW QFP e little history of iy nd relted projets F F F F F F F F F F F F F F F F SI QFPFI prom ix to iy R F F F F F F F F F F F F F F F F F F F F F F F SI QFPFP ide projets with iy F F F F F F F F F F F F F F F F F F F F F F F F SP QFQ heoretil frme of iy F F F F F F F F F F F F F F F F F F F F F F F F F F SQ QFQFI rton wodel F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F SR QFQFP qriovEegge heory F F F F F F F F F F F F F F F F F F F F F F F F F SR QFQFQ rtonEfsed qriovEegge heory F F F F F F F F F F F F F F F F F SS QFQFR tring wodel F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F SV QFR qenertion of n event in iy F F F F F F F F F F F F F F F F F F F F F F F SW s efvi yp gyxix QFS yjetives of the thesis F F F F F F F F F F F F F F F F F F F F F F F F F F F F F TQ QFSFI owrds the relese of iy R F F F F F F F F F F F F F F F F F F F F TQ QFSFP owrds the study of netEhrge umulnts F F F F F F F F F F F F F TR4 Technical developments for EPOS 4 67RFI si F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F TV RFIFI qenerl presenttion F F F F F F F F F F F F F F F F F F F F F F F F F F TV RFIFP he ene(ts for iy F F F F F F F F F F F F F F F F F F F F F F F F F UI RFP row iy works in prtie F F F F F F F F F F F F F F F F F F F F F F F F F UP RFPFI truture of the repository F F F F F F F F F F F F F F F F F F F F F F F UP RFPFP unning simultions F F F F F F F F F F F F F F F F F F F F F F F F F F UQ RFPFQ sing onEtheErun nlyses F F F F F F F F F F F F F F F F F F F F F F F US RFQ sntegrtion of si into iy nlysis frmework F F F F F F F F F F F F UU RFQFI roduing HepMC (les F F F F F F F F F F F F F F F F F F F F F F F F UU RFQFP eutomting the usge of Rivet F F F F F F F F F F F F F F F F F F F VQ RFQFQ heling with entrlity lirtion F F F F F F F F F F F F F F F F F F VT RFR ummry of the tehnil work F F F F F F F F F F F F F F F F F F F F F F F F VT5 Beam Energy Scan & study of cumulants with EPOS 89 SFI fsi spetr for the fi energies F F F F F F F F F F F F F F F F F F F F F F WI SFIFI seudorpidity densities of hrged hdrons F F F F F F F F F F F F F WI SFIFP rnsverse momentum spetr of identi(ed hdrons F F F F F F F F F WQ SFP tudy of the 2 nd order umulnts of onserved hrges F F F F F F F F F F F WW SFPFI esults for e proxiesX vrinesD ovrines nd their rtios F WW SFPFP gomprison with enhned proxies nd onserved hrges umulntsIHP SFPFQ smpt of hdroni sdes on the 2 nd order umulnts F F F F F F IHT SFQ ummry of results on 2 nd order umulnts study F F F F F F F F F F F F F F III Conclusion & Outlook A Transverse momentum spectra for identied hadrons B Centrality-Bin Width Correction C Net-multiplicity cumulants analysis in EPOS gFI ehnil implementtion of the nlysis F F F F F F F F F F F F F F F F F F F IPW gFP truture of the nlysis routine F F F F F F F F F F F F F F F F F F F F F F F IQH gFQ riting netEmultipliity umulnt nlysis F F F F F F F F F F F F F F F F F IQP D Cumulants of conserved charges before & after hadronic cascades E Résumé français de la thèse iFI gontexte et motivtions F F F F F F F F F F F F F F F F F F F F F F F F F F F F IQU iFP wotivtions et ojetifs de l thèse F F F F F F F F F F F F F F F F F F F F F F IRI iFQ héveloppements tehniques pour iy R F F F F F F F F F F F F F F F F F F IRQ iFR ésultts sur l9étude des umulnts de hrges onservées F F F F F F F F F IRS Acronyms List of Figures List of Tables

  Standard Model of particle physics . . . . . . . . . . . . . 1.1.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Limitations of the Standard Model . . . . . . . . . . . . . . . . 1.1.3 Beyond the Standard Model . . . . . . . . . . . . . . . . . . . . 1.2 Hadronic physics and Quantum ChromoDynamics . . . . . . 1.2.1 The foundation of QCD . . . . . . . . . . . . . . . . . . . . . . 1.2.2 How to deal with QCD: methods & phenomenological approaches II grei IF esgvi rsgX pyw riy y iiswix

Figure 1 . 1 :

 11 Figure 1.1: Components of the Standard Model listed with their main properties (mass, spin and electric charge) [15] taken from the Particle Data Group 2022 [14].

Figure 1 . 2 :

 12 Figure 1.2: Illustration of the J = 0 and J = 1/2 octets as representations of the SU(3) group.

Figure 1 . 3 :

 13 Figure 1.3: The intensity of the running coupling constant α s as a function of the virtuality Q of the process considered. Analytical prediction based on the renormalisation scale of the order of M Z , and values extracted from dierent processes are also displayed [14].

Figure 2

 2 Figure 2.1: Description of the evolution of the system created in HICs, in a space-time diagram, following the Björken scenario. The t and z coordinates are in Euclidean space-time, while the τ = √ t 2 -z 2 is in Milne coordinate [99].

Figure 2 . 2 :

 22 Figure 2.2: Timeline of the dierent experiments which took place at the CERN Super Proton Synchrotron (SPS), with the dierent ion beams used to collide on various targets, with the main topics of interest specied on top of the corresponding boxes [100].

Figure 2

 2 Figure 2.3: The semi-hypothetical phase diagram of nuclear matter sketched as a function of temperature T and baryonic chemical potential µ B . Exact position of phase transitions and critical point are approximate, just displayed to illustrate roughly the main structures [117].

Figure 2 . 4 :

 24 Figure 2.4: Distribution of the total inelastic cross-section as a function of the number of charged particles N ch produced by a collision within the |η| < 1 region. A correspondence with the integrated percentage of the total cross-section, used to determine the centrality percentage, is added. Values used on both axes are arbitrary and purely indicative [138].

Figure 2 . 5 :

 25 Figure 2.5: Phase diagram of nuclear matter, with representations of the trajectories described by several collisions systems of the BES program. Positions of phase transitions and critical point are purely illustrative [151]. o do soD euEeu ollisions hve een performed t √ s N N = 7.7D IIFSD IRFSD IWFTD PUD QWD SRFRD TPFR nd 200 qe in the (rst phse of the progrmF he systems thus reE ted re supposed to spn rnge 25 ≲ µ B ≲ 420 weD s deresing the em energy inreses the ryon hemil potentil ISIF sn seond phseD nmed fiEssD the e'ort hve een foused on the lowest em energies @< 20 qeGeAD s numerous results point out intriguing ehviours of the system reted in suh ollisions ISIF pigure PFS illustrtes the sn of the phse digrm mde possile y the fi progrmD in shemti fshionF he red dots indite vlues of freezeEout prmeters extrted from euEeu ollisions dt t the orresponding energyF o extend even further this prospeE tionD (xedEtrget euEeu ollisions were hieved down to 3.0 qeGe in the lst few yersD y the e experimentD in order to etter hrterise the onset of deon(nement ISPF

  Figure 2.6: K/π ratios measured within |y| < 1 in 0-5% Au-Au collisions as a function of the collision energy [177].

Figure 2

 2 Figure 2.7: 3D representation of the behaviour of χ B 2 as a function of T and µ B , for an equation of state containing a CEP at coordinates T CEP = 143 MeV and µ CEP B = 350 MeV. The divergence of χ B 2 around this location is indicated [218].

Figure 2

 2 Figure 2.8: Left: cumulant ratio C 4 /C 2 (= κσ 2 ) for net-protons, measured by STAR as a function of energy for central (0-5%) Au-Au collisions, compared to the linear Poisson baseline in the lower panel [214]. Right: expected behaviour of C 4 /C 1 (= ω 4 ) for net-protons, in the case of a freeze-out line passing through the critical region near the CEP (modied from [151]).

Figure 2 . 9 :

 29 Figure 2.9: Centrality dependence of the covariances of p, K and π net-multiplicity distributions, for Au-Au collisions at several indicated energies of the BES program, within |η| < 0.5 and 0.4 < p T < 1.6 GeV. Results from STAR, with systematic errors indicated by the boxes, are compared to CLT expectations and UrQMD simulations results [211].

  Figure 2.10: Energy dependence of the cumulants ratios C pK , C QK for central (0-5%) and peripheral (70-80%) Au-Au collisions, within |η| < 0.5 and 0.4 < p T < 1.6 GeV. Results from STAR have systematic errors indicated by the boxes and statistical ones by bars. Poisson baseline, UrQMD simulations results and calculations using HRG model including the PDG16+ [236] particles set are displayed for comparison [211].

Figure 2 .

 2 Figure 2.11: Breakdown of hadronic contribution to χ QS 11 and χ S 2 as a function of T , obtained with HRG model calculations [234].

Figure 2 .

 2 Figure 2.12: Comparison of several proxy ratios for QS and BS correlations obtained via HRG model calculations. Both are plotted as a function of T , with their related ratio of exact susceptibilities calculated with lQCD [234].

3. 3

 3 .1 Parton Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Gribov-Regge Theory . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Parton-Based Gribov-Regge Theory . . . . . . . . . . . . . . . 3.3.4 String Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Generation of an event in EPOS . . . . . . . . . . . . . . . . . 3.5 Objectives of the thesis . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Towards the release of EPOS 4 . . . . . . . . . . . . . . . . . . 3.5.2 Towards the study of net-charge cumulants . . . . . . . . . . . RU grei QF ri iy iix qixiey

Figure 3

 3 Figure 3.2: Timeline of the dierent versions of VENUS, neXus, EPOS and side-projects, based on the publication date of the rst papers mentioning them. (N.B. : EPOS-LHC [272] was released as a stable version, no longer developed after then)

Figure 3

 3 Figure 3.3: Diagram of a A-A collision viewed by the PBGRT formalism (original gure from [284])

Figure 3 . 4 :

 34 Figure 3.4: The ve dierent structures of Pomerons considered in the PBGRT, corresponding respectively to (from left to right): G sof t , G val-val , G sea-sea , G val-sea and G sea-val [284].

Figure 3

 3 Figure 3.5: Schematic view of a cut Pomeron as a cut parton ladder, used to model particle production in the PBGRT. The blue lines are the initial interacting partons, the curly lines are gluons and straight lines quarks [290, 291] sn the se of AEA ollision etween two nulei A nd BD the totl rossEsetion σ AB tot

Figure 3

 3 Figure 3.7: Schematic representation of the breaking of an initial u-ū string with the corresponding hadrons identied to the string segments obtained.

Figure 3

 3 Figure 3.8: Illustration of HQs production in space-like cascade (SLC), time-like cascade (TLC) and Born process during the primary interactions of a A-A collision with EPOS. Thick blue lines represent nucleons, while thin blue lines are drawn for partons [291].

Contents 4 .

 4 1 RIVET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.1.1 General presentation . . . . . . . . . . . . . . . . . . . . . . . . 68 4.1.2 The benets for EPOS . . . . . . . . . . . . . . . . . . . . . . . 71 4.2 How EPOS works in practice . . . . . . . . . . . . . . . . . . . 72 4.2.1 Structure of the repository . . . . . . . . . . . . . . . . . . . . 72 4.2.2 Running simulations . . . . . . . . . . . . . . . . . . . . . . . . 73 4.2.3 Using on-the-run analyses . . . . . . . . . . . . . . . . . . . . . 75 Writing an analysis in EPOS . . . . . . . . . . . . . . . . . . . 75 Centrality denitions in analyses . . . . . . . . . . . . . . . . . 76 4.3 Integration of RIVET into EPOS analysis framework . . . . 77 4.3.1 Producing HepMC les . . . . . . . . . . . . . . . . . . . . . . 77 Structure of HepMC event records . . . . . . . . . . . . . . . . 77 Production of HepMC output les with EPOS . . . . . . . . . 78 Content of the EPOS HepMC output . . . . . . . . . . . . . . 81 4.3.2 Automating the usage of Rivet . . . . . . . . . . . . . . . . . 83 Adapting the experimental data format . . . . . . . . . . . . . 83 Using Rivet from the EPOS analysis system . . . . . . . . . . 84 4.3.3 Dealing with centrality calibration . . . . . . . . . . . . . . . . 86 4.4 Summary of the technical work . . . . . . . . . . . . . . . . . . 86 TU grei RF igrxsgev hiivywix py iy R

Figure 4 . 1 :

 41 Figure 4.1: Schematic representation of the principal components of Rivet acting in the data ow from event record to results of the analysis, with the links between classes (in blue), les (in yellow) and the dierent commands (in green) used to execute it [303].

Figure 4 .

 4 Figure 4.2: RIVET analysis coverage compared to the total number of publications for LHC, SPS and RHIC experiments [305].

Figure 4 .

 4 Figure 4.3: Non-exhaustive structure of the directories containing the EPOS code.

  4.2.2 Running simulations sn order to run simultions with iyD one hs to de(ne the prmeters of the olE lision in (le with .optns extensionF ome exmples of suh (les n e found in the EPOS/Misc2/ repositoryD under the nmes expl[...].optnsF s will disuss here si exmple of (le de(ning simultions of euEeu ollisions t n energy of √ s N N = 200

Figure 4 . 4 :

 44 Figure 4.4: Example of instructions used in a .optns le to dene a simulation for Au-Au collisions.

Figure 4 .

 4 Figure 4.5: Example of an analysis dened in a .optns le to get a p T distribution of π + .

Figure 4 . 6 :

 46 Figure 4.6: Example of the content of a HepMC le for a Pb-Pb collision at 2.76 GeV/A.

  @RFQFPA reneD s the only essile prtiles informtion provided re the mss nd momentum VH RFQF sxiqesyx yp si sxy iy exevs pewiyu oordintesD one n otin rpidity strting from eqution RFQFI ginX p z e y + e -y = E e y -e -y ←→ p z 2 e y + e -y 2 = (m T 2 + p z 2 ) e y -e -y 2 , ←→ p z 2 e y + e -y 2 -e y -e -y 2 = m T 2 e y -e -y 2 , ←→ p z 2 × 4 = m T 2 e y -e -y 2 , ←→ p z = m T . sinh(y),

  -! Figure 02.01.01 ! Title : $\pi^-$ (Au+Au 7.7 GeV) ! X : $\pT$ (GeV/c) ! Y : $\frac{1}{2\pi}\frac{dN}{\pT d\pT}$ [(GeV/c)$^{-2}$] ! ! x xerr-xerr+ y yerr-yerr+ !-

Figure 4 . 8 :

 48 Figure 4.8: Example of an analysis dened in a .optns le to get a p T distribution of π + .

Figure 4 . 9 :

 49 Figure 4.9: Example of the instructions to write in a .optns le to run Rivet.

Figure 4 . 10 :

 410 Figure 4.10: Functional diagram of data & processes ow when calling Rivet through the EPOS analysis system.

2

  Figure 5.1: Pseudorapidity densities of charged particles for Au-Au collisions at √ s N N = 19.6, 62.4 and 200 GeV, in dierent centrality classes within 0-50%. Results from EPOS 3.451 are compared with data from PHOBOS, results from dierent centrality classes being displayed alternatively in two plots per energy for visibility [309].

Figure 5 . 2 :

 52 Figure 5.2: Transverse momentum spectra of π ± , K ± and p/p within |η| < 0.35, for dierent centrality classes in Au-Au events at √ s N N = 200 GeV. Spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4}) (data from [310]).

Figure 5 . 3 :

 53 Figure 5.3: Transverse momentum spectra of π ± , K ± and p/p at y = 0.8, for dierent centrality classes in Au-Au events at √ s N N = 62.4GeV. Spectra for the most central events are at real scale, while the others are scaled by factors 10 -1 (15-30%) and 10 -2 (30-50%) (data from[311]).

Figure 5 . 4 :

 54 Figure 5.4: Transverse momentum spectra of Λ, Λ, Ξ -, Ξ + and Ω -+ Ω + for dierent centrality classes in Au-Au events at √ s N N = 200 GeV. Spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4}) (data from [313]).

Figure 5 . 5 :

 55 Figure 5.5: Transverse momentum spectra of Λ, Λ, Ξ -, Ξ + , Ω -and Ω + for dierent centrality classes in Au-Au events at √ s N N = 27 GeV. Spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4, 5, 6}) (data from [315]).

Figure 5

 5 Figure 5.7: Net-p, net-K and net-π multiplicity variances vs. N part for dierent energies, obtained from EPOS 3.451 simulations (red lines) and compared with STAR results (dots) [211].

Figure 5

 5 Figure 5.8: Net-p, net-K and net-π multiplicity covariances vs. N part for dierent energies, obtained from EPOS 3.451 simulations (red lines) and compared with STAR results (dots) [211].

Figure 5

 5 Figure 5.9: Ratios of net-p, net-K and net-π multiplicity (co)variances vs. N part for dierent energies, obtained from EPOS 3.451 simulations (red lines) and compared with STAR results (dots) [211].

Figure 5 . 10 :

 510 Figure 5.10: Breakdown of hadronic contribution to χ 11 QB and χ 2 B as a function of T , obtained with HRG model calculations [234].

Figure 5 .

 5 Figure 5.11: Ratios of exact B, Q and S conserved charges (co)variances and their proxies displayed as a function of N part for dierent energies, obtained from EPOS 3.451 simulations (lines) and compared with STAR data (dots) as an indication [211].

Figure 5 .

 5 Figure 5.12: Ratios of exact B, Q and S conserved charges (co)variances and their proxies displayed as a function of √ s N N for central (left) and peripheral (right) collisions. Results from EPOS 3.451 simulations (lines), compared with STAR data (dots) as an indication [211].

Figure 5 .

 5 Figure 5.13: Net-p, net-π, net-K and net-Λ multiplicity variances vs. N part for dierent energies, obtained from EPOS 3.451 simulations and compared with STAR results (dots) [211].The results calculated from full events are represented by full lines, while results calculated before hadronic cascades are represented by dotted lines.

Figure 5 .

 5 Figure 5.15: Ratios of exact B, Q and S conserved charges (co)variances and their proxies plotted as a function of √ s N N for central (left) and peripheral (right) collisions. Results are displayed for full event calculation (full lines) and calculation before hadronic cascades (dotted lines) from EPOS 3.451 simulations. STAR data (dots) are shown as an indication [211].

Figure 5 .

 5 Figure 5.16: Ratios of C XY and enhanced proxies CXY calculated before hadronic cascades over full event calculations, plotted as a function of √ s N N for central (left) and peripheral collisions (right).

Figure A. 1 :

 1 Figure A.1: Transverse momentum spectra of respectively line by line π + , π -, K + and K -, at |y| < 0.1, for centrality classes from 0% to 40% (left) and 40% to 80% (right) in Au-Au events at √ s N N = 27 GeV. In each plot, spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4}) (data from [177]).

Figure A. 2 :

 2 Figure A.2: Same than previous gure but for p and p.

Figure A. 3 :

 3 Figure A.3: Transverse momentum spectra of respectively line by line π + , π -, K + and K -, at |y| < 0.1, for centrality classes from 0% to 40% (left) and 40% to 80% (right) in Au-Au events at √ s N N = 14.5 GeV. In each plot, spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4}) (data from[177]).

Figure A. 4 :

 4 Figure A.4: Same than previous gure but for p and p.

Figure A. 5 :

 5 Figure A.5: Transverse momentum spectra of respectively line by line π + , π -, K + and K -, at |y| < 0.1, for centrality classes from 0% to 40% (left) and 40% to 80% (right) in Au-Au events at √ s N N = 7.7 GeV. In each plot, spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4}) (data from[177]).

Figure A. 6 :

 6 Figure A.6: Same than previous gure but for p and p.

Figure A. 7 :

 7 Figure A.7: Transverse momentum spectra of Λ, Λ, Ξ -, Ξ + , Ω -and Ω + for dierent centrality classes in Au-Au events at √ s N N = 19.6 GeV. Spectra for the most central events are at real scale, while the others are scaled by factors 10 -x (x = {1, 2, 3, 4, 5, 6}) (data from [315]).

Figure

  Figure B.1: Centrality dependence of net-p, net-K and net-π multiplicity variances for Au+Au collisions at √ s N N = 200 GeV, obtained from EPOS 3.451 simulations. The lines represent cumulant calculations as a function of the N part variable directly, while the point represent cumulants calculated for usual STAR centrality classes (i.e. 0-5%, 5-10%, 10-20%...70-80%) [211].

Figure B. 2 :

 2 Figure B.2: Centrality dependence of net-p, net-K and net-π multiplicity covariances for Au+Au collisions at √ s N N = 200 GeV, obtained from EPOS 3.451 simulations. The lines represent cumulant calculations as a function of the N part variable directly, while the point represent cumulants calculated for usual STAR centrality classes (i.e. 0-5%, 5-10%, 10-20%...70-80%) [211].

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  RFW ixmple of the instrutions to write in .optns (le to run ivetF F F F F VU RFIH puntionl digrm of dt 8 proesses )ow when lling ivet through the iy nlysis systemFF F F F F F F F F F F F F F F F F F F F F F F F F FVV SFI seudorpidity densities of hrged prtiles for euEeu ollisions t √ s N N = 19.6D TPFR nd PHH qeD in di'erent entrlity lsses within HESH7F eE sults from iy QFRSI re ompred with dt from ryfyD results from di'erent entrlity lsses eing displyed lterntively in two plots per energy for visiility QHWF F F F F F F F F F F F F F F F F F F F F F F F F F WP SFP rnsverse momentum spetr of π ± D K ± nd p/p within |η| < 0.35D for di'erent entrlity lsses in euEeu events t √ s N N = 200 qeF petr

  entrlity lsses in euEeu events t √ s N N = 7.7 qeF petr for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4, 5, 6}A @dt from QISAF F F F F F F F F F F F F F F F F WV SFU xetEpD netEK nd netEπ multipliity vrines vsF N part for di'erent enE ergiesD otined from iy QFRSI simultions @red linesA nd ompred with e results @dotsA PIIFF F F F F F F F F F F F F F F F F F F F F FF IHH SFV xetEpD netEK nd netEπ multipliity ovrines vsF N part for di'erent energiesD otined from iy QFRSI simultions @red linesA nd ompred with e results @dotsA PIIF F F F F F F F F F F F F F F F F F F F F F F F IHI ISU vs yp psqi SFW tios of netEpD netEK nd netEπ multipliity @oAvrines vsF N part for di'erent energiesD otined from iy QFRSI simultions @red linesA nd ompred with e results @dotsA PIIFF F F F F F F F F F F F F F F F F F IHP SFIH frekdown of hdroni ontriution to χ 11 QB nd χ 2 B s funtion of T D otined with rq model lultions PQRF F F F F F F F F F F F F F F F F IHQ SFII tios of ext BD Q nd S onserved hrges @oAvrines nd theirproxies displyed s funtion of N part for di'erent energiesD otined from iy QFRSI simultions @linesA nd ompred with e dt @dotsA sn indition PIIF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F IHR SFIP tios of ext BD Q nd S onserved hrges @oAvrines nd theirproxies displyed s funtion of √ s N N for entrl @leftA nd peripherl @rightA ollisionsF esults from iy QFRSI simultions @linesAD ompred with e dt @dotsA s n indition PIIF F F F F F F F F F F F F F F F IHS SFIQ xetEpD netEπD netEK nd netEΛ multipliity vrines vsF N part for di'erE ent energiesD otined from iy QFRSI simultions nd ompred with e results @dotsA PIIF he results lulted from full events re repE resented y full linesD while results lulted efore hdroni sdes re represented y dotted linesFF F F F F F F F F F F F F F F F F F F F F F F F F F IHT SFIR govrines of netEpD netEπ nd netEK multipliity distriution vsF N partfor di'erent energiesD otined from iy QFRSI simultions nd omE pred with e results @dotsA PIIF he results lulted from full events re represented y full linesD while results lulted efore hdroni sdes re represented y dotted linesF F F F F F F F F F F F F F F F F F F IHU SFIS tios of ext BD Q nd S onserved hrges @oAvrines nd their proxies plotted s funtion of √ s N N for entrl @leftA nd peripherl @rightA ollisionsF esults re displyed for full event lultion @full linesA nd lultion efore hdroni sdes @dotted linesA from iy QFRSI simultionsF e dt @dotsA re shown s n indition PIIF F F F F F IHV SFIT tios of C XY nd enhned proxies CXY lulted efore hdroni sE des over full event lultionsD plotted s funtion of √ s N N for entrl @leftA nd peripherl ollisions @rightAF F F F F F F F F F F F F F F F F F F F F IHW SFIU gore proportion of C XY nd enhned proxies CXY rtios over the totl vlue lulted efore hdroni sdesD plotted s funtion of √ s N N

  F F F F F F F F F F F F F IPP ISV vs yp psqi eFT me thn previous (gure ut for p nd pF F F F F F F F F F F F F F F F F F IPQ eFU rnsverse momentum spetr of ΛD ΛD Ξ -D Ξ+ D Ω -nd Ω + for di'erent entrlity lsses in euEeu events t √ s N N = 19.6 qeF petr for the most entrl events re t rel sleD while the others re sled y ftors 10 -x @x = {1, 2, 3, 4, 5, 6}A @dt from QISAF F F F F F F F F F F F F F F F F IPR fFI gentrlity dependene of netEpD netEK nd netEπ multipliity vrines for euCeu ollisions t √ s N N = 200 qeD otined from iy QFRSI simultionsF he lines represent umulnt lultions s funtion of the N part vrile diretlyD while the point represent umulnts lulted for usul e entrlity lsses @i.e. HES7D SEIH7D IHEPH7FFFUHEVH7A PIIFF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F FIPT fFP gentrlity dependene of netEpD netEK nd netEπ multipliity ovrines for euCeu ollisions t √ s N N = 200 qeD otined from iy QFRSI simultionsF he lines represent umulnt lultions s funtion of the N part vrile diretlyD while the point represent umulnts lulted for usul e entrlity lsses @i.e. HES7D SEIH7D IHEPH7FFFUHEVH7A PIIFF F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F IPU hFI rines of BD Q nd SvsF N part for di'erent euEeu ollisions energiesD otined from iy QFRSI simultionsF he results lulted from full events re represented y full linesD while results lulted efore hdroni sdes re represented y dotted linesF F F F F F F F F F F F F F F F F F F IQS hFP govrines of BD Q nd S vsF N part for di'erent euEeu ollisions energiesD otined from iy QFRSI simultionsF he results lulted from full events re represented y full linesD while results lulted efore hdroni sdes re represented y dotted linesF F F F F F F F F F F F F F F F F F F IQT ISW ITH LIST OF TABLES SFI xumer of events simulted with iy QFRSI per ollision energyF F F F F WH gFI snput prmeters of the 4mupurp_susc()4 suroutine to perform luE ltion of moments from 1 st to 4 th order of netEmultipliity distriutionF F F IQH gFP gorrespondene etween digits nd ssoited hrge or prtile for xpara (9,n)F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F FIQH ITI ITP BIBLIOGRAPHY I tFtF homsonF Cathode RaysF snX The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science RRFPTW @IVWUAD ppF PWQ!QITF doiX 10. 1080/14786449708621070F P rF qeiger nd iF wrsdenF On a Diuse Reection of the α -ParticlesF snX Proceedings of the Royal Society of London Series A VPFSSU @tuly IWHWAD ppF RWS! SHHF doiX 10.1098/rspa.1909.0054F Q iF utherfordF The scattering of α and β particles by matter and the structure of the atomF snX Phil. Mag. Ser. 6 PI @IWIIAD ppF TTW!TVVF doiX 10.1080/14786440508637080F R wx lnkF Ueber das Gesetz der Energieverteilung im Normalspec-trumF snX Annalen der Physik QHWFQ @tnF IWHIAD ppF SSQ!STQF doiX 10.1002/ andp.19013090310F S eF iinsteinF Über einen die Erzeugung und Verwandlung des Lichtes betreenden heuristischen GesichtspunktF snX Annalen der Physik QPPFT @tnF IWHSAD ppF IQP!IRVF doiX 10.1002/andp.19053220607F T xiels fohrF I. On the constitution of atoms and moleculesF snX The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science PTFISI @IWIQAD ppF I!PSF doiX 10.1080/14786441308634955F U xiels fohrF XXXVII. On the constitution of atoms and moleculesF snX The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science PTFISQ @IWIQAD ppF RUT!SHPF doiX 10.1080/14786441308634993F V xiels fohrF LXXIII. On the constitution of atoms and moleculesF snX The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science PTFISS @IWIQAD ppF VSU!VUSF doiX 10.1080/14786441308635031F W olfgng uliF Pauli letter collection: letter to Lise MeitnerF urlX https: //cds.cern.ch/record/83282F IH inrio permiF Tentativo di una teoria dell'emissione dei raggi betaF snX Ric. Sci. R @IWQQAD ppF RWI!RWSF II tF ghdwikF Possible Existence of a NeutronF snX Nature IPW @IWQPAD pF QIPF doiX 10.1038/129312a0F

  On a theoretical level: from rst predictions to current models 22 2.1.1 The theoretical genesis behind the discovery of the QGP . . . . 22 2.1.2 The phase diagram of nuclear matter . . . . . . . . . . . . . . . 25 2.2 Studying the QGP at the experimental level . . . . . . . . . . 27 2.2.1 Kinematics of high-energy collisions . . . . . . . . . . . . . . . 27 2.2.2 The experimental apparatus . . . . . . . . . . . . . . . . . . . . 29 STAR results & enhanced proxies for 2 nd order cumulants . . . 41 Variances and covariances of net-Q, net-p and net-K multiplicity distributions . . . . . . . . . . . . . . . . . . . . . 41 New proxies for the ratios of 2 nd order susceptibilities . . . . . 44

	grei PF ri ryi wei yp ri xsii
	THE HOTTEST MATTER OF THE UNIVERSE
	Contents
	2.1 PI

The BES program at RHIC . . . . . . . . . . . . . . . . . . . . 29 Heavy-ions at CERN . . . . . . . . . . . . . . . . . . . . . . . . 31 Future facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 2.2.3 Methods to study the QGP . . . . . . . . . . . . . . . . . . . . 32 Soft probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Hard probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 2.3 Focus on: criticality in the nuclear phase diagram . . . . . . . 34 2.3.1 Thermodynamic susceptibilities and net-charge cumulants . . . 35 2.3.2 Limits and shortcomings of experimental and theoretical observables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 2.3.3

  nd used in the ll of 4ATLAS_2015_I13864754D is omptile with the nlysed set of eventsF reneD the (le pPb5T.optns should ontin wht is indited in (gure RFWF

	set ihepmc 1	! Activate HepMC production
	set rapcms -0.465	! CoM rapidity shift
	set ihepframe 1	! To apply shift on particle coordinates in HepMC
	! Centrality calibration(s)
	rivet calib_run ATLAS_pPb_Calib[mult]
	! Pseudorapidity density for charged particles
	rivet ATLAS_2015_I1386475 d02 calib:ATLAS_pPb_Calib

Table 5

 5

	1 IN2P3 Computing Centre
	WH

.1: Number of events simulated with EPOS 3.451 per collision energy.

Table C .

 C 1: Input parameters of the "mupurp_susc()" subroutine to perform a calculation of moments from 1 st to 4 th order of net-multiplicity distribution.

		Parameter value(s)	Parameter correspondence
	xpara(1,n)	IHHT	indites to ll 4mupurp_susc()4
	xpara(2,n)	[0, ∞] ∈ R	lowest p T vlue of prtiles to onsider
	xpara(3,n)	[0, ∞] ∈ R	highest p T vlue of prtiles to onsider
	xpara(4,n)	H I	ut pplied in rpidity y ut pplied in pseudorpidity η
	xpara(5,n)	[0, ∞] ∈ R	mximum |y/η| of prtiles to onsider
		H	no feedEdown orretion
	xpara(6,n)	I	geometril ut @hge< 1mA
		P	strit feedEdown orretion @≡ 4noweak4A
	xpara(7,n)	H I	onsiders only p prtiles C prents onsiders prtiles efore hdroni sde
		H	onsiders ll prtiles
	xpara(8,n)	I	onsiders prtile from the ore only
		P	onsiders prtile from the oron only
		a	indites to lulte δN 1 a
	xpara(9,n)	ab abc	indites to lulte δN 2 ab indites to lulte δN 3 abc
		abcd	indites to lulte δN 4 abcd

  in order to otin the vrineD one simply needs to pply the formul @PFQFIRAD done with the ommnds displyed in the next frmeF he histogrm otined is lso omplemented with instrutions for the plottingD i.e. xes lels @N part nd σ 2 p for x nd y xes respetivelyD in the e lngugeAF he (rst opertion hieved with 4calc4 lultes ⟨δN p ⟩ 2 D nd the seond gives σ 2 p = ⟨δN p 2 ⟩ -⟨δN p ⟩ 2 F Contexte et motivations . . . . . . . . . . . . . . . . . . . . . . 137 E.2 Motivations et objectifs de la thèse . . . . . . . . . . . . . . . . 141 E.3 Développements techniques pour EPOS 4 . . . . . . . . . . . . 143 E.4 Résultats sur l'étude des cumulants de charges conservées . . 145

	gFQF ssxq e xiEwvsvsgs gwvex exevs
	beginhisto
	histogram npnevt ncum-evt 4 0.5 400.5 40
	xparas 9 1006 0.4 1.6 1 0.5 1 0 0 66
	trigger bimevt bim00 bim80
	endhisto beginwrite APPENDIX E
	openhisto name Npart-ncum-pp
	[[histoweight writearray 3]] closehisto	RÉSUMÉ FRANÇAIS DE LA THÈSE
	endwrite
	Contents
	E.1
	beginwrite
	openhisto name Npart-variance-pp htyp lin
	txt ""xaxis N?part!""
	txt ""yaxis green: [s]?B!&^2!""
	calc Npart-ncum-p * Npart-ncum-p ; -> 1
	calc Npart-ncum-pp -$1 ;
	closehisto plot 0
	endwrite
			ith the following instrutionsD one n then
	lulte ⟨δN p	2 ⟩ for the ext sme seletion riteriF
			IQP

pinllyD

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rivX 1805.04432 [nucl-ex]F

Space-time rapidity, dened as ς = 1

ln [(t + z)/(t -z)]

Note that, following the convention from the STAR paper, C αβ refers here to ratios of cumulants and not to cumulants themselves, as it was the case in subsection 2.3.1. As from now on we will only discuss 2 nd order cumulants, i.e. (co)variances σ 2/11 , we will keep this convention of C αβ designating cumulants ratios for the whole manuscript.

https://www.hepdata.net/

https://rivet.hepforge.org/

Title :

The Beam Energy Scan under the scope of EPOS 4 -Studying the impact of hadronic cascades on the 2 nd order cumulants of conserved net-charges in heavy-ion collisions Keywords : Heavy-Ion Collisions, Quark-Gluon Plasma, Critical Endpoint, EPOS Event Generator,

RIVET analysis toolkit

Abstract : During the last two decades, heavy-ion collisions at ultra-relativistic energies have been used to investigate the properties of the Quark-Gluon Plasma (QGP), a state of matter in which quarks & gluons are deconfined from hadrons. One of the major goals of this research is to map the phase diagram of nuclear matter, made possible experimentally thanks to the Beam Energy Scan (BES) program. It is performed, among other objectives, to search for a 1 st order phase transition and a critical endpoint between QGP and hadron gas phases. Ratios of net-multiplicities cumulants has been shown to be relevant experimental proxies for such study, due to their link with thermodynamic susceptibilities. In this regard, the STAR collaboration has recently published measurements of the 2 nd order cumulants of net-multiplicities for pions, kaons and protons in Au+Au collisions at several energies of the BES program. However, signatures from a 1 st order transition or a critical point may be blurred out by the last stages of the collision. Taking advantage of the modular conception of the EPOS event generator, the impact of the hadronic cascades on these 2 nd order cumulants has been studied. The STAR proxies results are also compared with the 2 nd order cumulants of the corresponding conserved charges, and with enhanced proxies proposed by the authors of a study based on lattice quantum chromodynamics calculations and the use of a Hadron Resonance Gas model. This work takes place in the context of developments for a new version of EPOS, what requires to validate its reliability by comparing simulations with experimental data for a wide range of systems and beam energies. The integration of the RIVET analysis toolkit, which has been achieved to facilitate this validation process, is also presented in this thesis.