Multiphasetransportmodelforrelativisticheavyioncol

PHYSICALREVIEWC72,064901(2005)MultiphasetransportmodelforrelativisticheavyioncollisionsZi-WeiLin∗PhysicsDepartment,TheOhioStateUniversity,Columbus,Ohio43210,USACheMingKoCyclotronInstituteandPhysicsDepartment,TexasA&MUniversity,CollegeStation,Texas77843,USABao-AnLiandBinZhangDepartmentofChemistryandPhysics,ArkansasStateUniversity,StateUniversity,Arkansas72467,USASubrataPalDepartmentofPhysics,MichiganStateUniversity,EastLansing,Michigan48824,USA(Received30November2004;published8December2005)Wedescribeindetailhowthedifferentcomponentsofamultiphasetransport(AMPT)modelthatusestheheavyionjetinteractiongenerator(HIJING)forgeneratingtheinitialconditions,Zhang’spartoncascade(ZPC)formodelingpartonicscatterings,theLundstringfragmentationmodeloraquarkcoalescencemodelforhadronization,andarelativistictransport(ART)modelfortreatinghadronicscatteringsareimprovedandcombinedtogiveacoherentdescriptionofthedynamicsofrelativisticheavyioncollisions.Wealsoexplainthewayparametersinthemodelaredeterminedanddiscussthesensitivityofpredictedresultstophysicalinputinthemodel.Comparisonsoftheseresultstoexperimentaldata,mainlyfromheavyioncollisionsattheBNLRelativisticHeavyIonCollider,arethenmadeinordertoextractinformationonthepropertiesofthehotdensematterformedinthesecollisions.DOI:10.1103/PhysRevC.72.064901PACSnumber(s):25.75.−q,12.38.Mh,24.10.LxI.INTRODUCTIONCollidingheavyionsatrelativisticenergiesmakesitpossibletosubjectnuclearmattertotheextremeconditionoflargecompression,leadingtoenergydensitiesthatcanexceedthatforproducingaplasmaofdeconfinedquarksandgluons,whichisbelievedtohaveexistedduringthefirstmicrosecondaftertheBigBang.ExperimentsattheBNLRelativisticHeavyIonCollider(RHIC)withcenter-of-massenergyupto√sNN=200GeVinAu+Aucollisionsthusprovidetheopportunitytostudythepropertiesofthisso-calledquark-gluonplasma(QGP).AtthefutureLargeHadronCollider(LHC)atCERN,whichwillallowPb+Pbcollisionsat√sNN=5.5TeV,theproducedquark-gluonplasmawillhaveanevenhighertemperatureandanearlyvanishingnetbaryonchemicalpotential.ManyobservableshavebeenmeasuredatRHIC,suchastherapiditydistributionsofvariousparticlesandtheirtransversemomentumspectrauptoveryhightransversemomentum,thecentralitydependenceoftheseobservables,andtheellipticflowsofvariousparticles,aswellasbothidenticalandnonidenticaltwo-particlecorrelations.Tounderstandtheseextensiveexperimentalresults,manytheoreticalmodelshavebeenintroduced.Theyrangefromthermalmodels[1–4]basedontheassumptionofglobalthermalandchemicalequilibrium,tohydrodynamicmodels[5–11]basedonlyontheassumptionoflocalthermalequilibrium,totransportmodels[12–26]thattreatnonequilibriumdynamicsexplicitly.Thethermal∗Presentaddress:301SparkmanDrive,VBRHE-39,UniversityofAlabamainHuntsville,Huntsville,AL35899.modelshavebeenverysuccessfulinaccountingfortheyieldofvariousparticlesandtheirratios,whilethehydrodynamicmodelsareparticularlyusefulforunderstandingthecollectivebehavioroflowtransversemomentumparticlessuchastheellipticflow[8–11].Sincetransportmodelstreatchemicalandthermalfreeze-outdynamically,theyarealsonaturalandpowerfultoolsforstudyingtheHanbury-Brown-Twissinter-ferometryofhadrons.Forhardprocessesthatinvolvelargemomentumtransfer,approachesbasedontheperturbativequantumchromodynamics(pQCD)usingpartondistributionfunctionsinthecollidingnucleihavebeenused[27,28].Also,theclassicalYang-Millstheoryhasbeendevelopedtoaddresstheevolutionofpartondistributionfunctionsinnucleiatultrarelativisticenergies[29–31]andusedtostudythehadronrapiditydistributionanditscentralitydependenceatRHIC[32–34].TheseproblemshavealsobeenstudiedinthepQCD-basedfinal-statesaturationmodel[35–37].AlthoughstudiesbasedonthepQCD[38]haveshownthatthermalizationcouldbeachievedincollisionsofverylargenucleiand/oratextremelyhighenergy,eventhoughthestrongcouplingconstantatthesaturationscaleisasymptoticallysmall,thedensemattercreatedinheavyioncollisionsatRHICmay,however,notachievefullthermalorchemicalequilibriumasaresultofitsfinitevolumeandenergy.Toaddresssuchnonequilibriummany-bodydynamics,wehavedevelopedamultiphasetransport(AMPT)modelthatincludesbothinitialpartonicandfinalhadronicinteractionsandthetransitionbetweenthesetwophasesofmatter[39–50].TheAMPTmodelisconstructedtodescribenuclearcollisionsrangingfromp+AtoA+Asystemsatcenter-of-massenergiesfromabout√sNN=5to5500GeVatLHC,where0556-2813/2005/72(6)/064901(29)/$23.00064901-1©2005TheAmericanPhysicalSocietyLIN,KO,LI,ZHANG,ANDPALPHYSICALREVIEWC72,064901(2005)stringsandminijetsdominatetheinitialenergyproductionandeffectsfromfinal-stateinteractionsareimportant.Fortheinitialconditions,theAMPTmodelusesthehardminijetpartonsandsoftstringsfromtheheavyionjetinteractiongenerator(HIJING)model.Zhang’spartoncascade(ZPC)isthenusedtodescribescatteringsamongpartons,whichisfollowedbyahadronizationprocessbasedontheLundstringfragmentationmodelorbyaquarkcoalescencemodel.ThelatterisintroducedforanextendedAMPTmodelwithstringmeltinginwhichhadrons,whichwouldhavebeenproducedfromstringfragmentation,areconvertedinsteadtotheirvalencequarksandantiquarks.Scatteringsamongtheresultin