第十届全国粒子物理大会桂林

Effectofequilibriumphasetransitionon

multiphasetransportinrelativisticheavyioncollisions喻梅凌华中师范大学粒子物理研究所2/27/20231第十届全国粒子物理大会桂林IntroductionandmotivationAMPTmodelandthetimeevolutionCollectivephasetransitionanditseffectConclusionoutline2I.Introductionandmotivation

Stagesofheavyioncollisionanddifferenttheoreticalapproach3BasicideasofMonteCarlosimulationabouttransporttheoryNecessitytocombinetransportmodelwithphasetransitionInheavyionsimulation,whencollectivephenomenonemerge,transportisn’tenought

PartonphaseisinpQCDvacuum,whilehadronphaseisinphysicalvacuum

Transporttheorydescribestheevolutionofparton

distribitioninphasespacetransportequationsarenumericallysolvedbysimulatingthedynamicalevolutionofthepartondistributionsasasuccessionofbinaryparton-partoncollisionsThemechanicsaboutthermalizationandformationofQGParestudiedinmicroscopic4II.AMPTmodelandthetimeevolution

ComponentsofA

MultiPhase

TransportModel(AMPTv2.11)AMPTv2.11wassuccessfulinellipticflowandHBTbutfailedtodescribehadronrapidityandtransversemomentumspectra

Initialconditions:(x,p)distributionsofminijet

partonsfromhardprocessandstringsfromsoftprocess,stringsaremeltedtobepartons

Partonictransport:onlytwo-bodyelasticscatteringstwopartonscollideif

Hadronization:

Hadrontransport:Z.W.Linetal.PRC72(2005)064901AuAucollisionat200AGeV,impactparameterb<3fm,partoncrosssection10mb5

PartonandhadrontimeevolutioninAMPTv2.11

Partonformationtime:

Thepercentageofpartonandhadronvarieswithtime:Whent<5fm/c,partondominate,systemindeconfinedphaseWhent>30fm/c,hadrondominate,systeminconfinedphaseProblemsoccur:1)somepartonshaveunreasonablelonglifetime2)deconfined

partonsexistinconfinedphysicalvacuum3)parton-wisehadronizationbutnocollectivephasetransition

Whenpartoninteractioncease,hadronsareproducedonebyone6III.Collectivephasetransitionanditseffect

ExtracttemperaturefromparticlespectrumAssumelocallythermalequilibrium,inathermal+transverseradialflowmodel,thetransversemassdistributionisT:kineticfreezeouttemperature,Latticepredictedcriticaltemperature7Collectivephasetransitionfollowingasuper-coolingstageTosolvetheproblemofAMPT,wehaveaphysicalpicture:

1)HightemperatureQGPexpandsandevaporateshadrons2)Thesystemsupercoolstoapoint(modelparameter)lowerthan3)AsuddenphasetransitionturnsalltheleftpartonstohadronsatthispointThetimeevolutionofpartonandhadrontemperature

withphasetransitionatt=5fm/chadronphasepartonphase8Theeffectofcollectivephasetransitiononfinalstatedistribution1)hadronrapiditydistributionAMPTwithphasetransitiondescribesdatabetter

92)Ellipticflow10IV.Conclusion

UnreasonablelonglifetimeofpartonsisfoundintransportmodelTosolvetheproblem,acollectivephasetransitionisaddedtothetransportmodelAMPTtoreplacetheparton-wisehadronizationBettermodelanddataagreementareachievedforthelongitudinaldistributionandellipticflowCollectivephasetransitionisnecessaryfortransportmodel1112II.AMPTmodelandthetimeevolution

ComponentsofAMultiPhaseTransportModel(AMPTv2.11)

Initialconditions:spatialandmomentumdistributionsofminijet

partonsfromhardprocessandstringsfromsoftprocess,stringsaremeltedtobepartons

Partonictransport:onlytwo-bodyelasticscatteringsareconsideredwithcrosssection.Twopartonswillundergoscatteringwhentheclosestdistancebetweenthemissmallerthan

Hadronization:

Hadrontransport:AMPTv2.11wassuccessfulinellipticflowandHBTbutfailedtodescribehadronrapidityandtransversemomentumspectra

13BasicideasofMonteCarlosimulationabouttransporttheory

Semi-classically,partondensitydistributioninphasespacecanbedescribedbyBoltzmanequation

BoltzmanequationaresolvedbysimulatingtheinteractionandevolutionofpartonsindetailThemechanicsaboutthermalizationandformationofQGParestudied