Phi meson production in Au+Au and p+p collisions at sqrt (s)

We report the STAR measurement of Phi meson production in Au+Au and p+p collisions at sqrt (s)=200 GeV. Using the event mixing technique, the Phi spectra and yields are obtained at mid-rapidity for five centrality bins in Au+Au collisions and for non-singl

φmesonproductioninAu+Auandp+pcollisionsat

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arXiv:nucl-ex/0406003v2 7 Jun 2004

We report the STAR measurement of Phi meson production in Au+Au and p+p collisions at sqrt (s)=200 GeV. Using the event mixing technique, the Phi spectra and yields are obtained at mid-rapidity for five centrality bins in Au+Au collisions and for non-singl

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BrookhavenNationalLaboratory,Upton,NewYork11973UniversityofBirmingham,Birmingham,UnitedKingdom4

UniversityofCalifornia,Berkeley,California947205

UniversityofCalifornia,Davis,California956166

UniversityofCalifornia,LosAngeles,California900957

CaliforniaInstituteofTechnology,Pasadena,California911258

CarnegieMellonUniversity,Pittsburgh,Pennsylvania15213

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CreightonUniversity,Omaha,Nebraska68178

10ˇz/Prague,CzechRepublicNuclearPhysicsInstituteASCR,Reˇ

11

LaboratoryforHighEnergy(JINR),Dubna,Russia12

ParticlePhysicsLaboratory(JINR),Dubna,Russia13

UniversityofFrankfurt,Frankfurt,Germany14

IndianInstituteofTechnology,Mumbai,India15

IndianaUniversity,Bloomington,Indiana4740816

InstituteofPhysics,Bhubaneswar751005,India17

InstitutdeRecherchesSubatomiques,Strasbourg,France

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UniversityofJammu,Jammu180001,India19

KentStateUniversity,Kent,Ohio44242

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LawrenceBerkeleyNationalLaboratory,Berkeley,California94720

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Max-Planck-Institutf¨urPhysik,Munich,Germany22

MichiganStateUniversity,EastLansing,Michigan4882423

MoscowEngineeringPhysicsInstitute,MoscowRussia24

CityCollegeofNewYork,NewYorkCity,NewYork10031

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NIKHEF,Amsterdam,TheNetherlands26

OhioStateUniversity,Columbus,Ohio4321027

PanjabUniversity,Chandigarh160014,India

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PennsylvaniaStateUniversity,UniversityPark,Pennsylvania16802

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InstituteofHighEnergyPhysics,Protvino,Russia30

PurdueUniversity,WestLafayette,Indiana4790731

UniversityofRajasthan,Jaipur302004,India32

RiceUniversity,Houston,Texas7725133

UniversidadedeSaoPaulo,SaoPaulo,Brazil

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UniversityofScience&TechnologyofChina,Anhui230027,China35

ShanghaiInstituteofNuclearResearch,Shanghai201800,P.R.China

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SUBATECH,Nantes,France

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TexasA&MUniversity,CollegeStation,Texas77843

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UniversityofTexas,Austin,Texas7871239

ValparaisoUniversity,Valparaiso,Indiana4638340

VariableEnergyCyclotronCentre,Kolkata700064,India41

WarsawUniversityofTechnology,Warsaw,Poland42

UniversityofWashington,Seattle,Washington9819543

WayneStateUniversity,Detroit,Michigan48201

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InstituteofParticlePhysics,CCNU(HZNU),Wuhan,430079China

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YaleUniversity,NewHaven,Connecticut0652046

UniversityofZagreb,Zagreb,HR-10002,Croatia

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WereporttheSTARmeasurementofφmesonproductioninAu+Auandp+pcollisionsat

We report the STAR measurement of Phi meson production in Au+Au and p+p collisions at sqrt (s)=200 GeV. Using the event mixing technique, the Phi spectra and yields are obtained at mid-rapidity for five centrality bins in Au+Au collisions and for non-singl

mationwithoutperturbationsfromco-movinghadrons.Forthesereasons,φproductioninrelativisticnuclearcol-lisionshasbeenofgreatinterest.

Themechanismforφproductioninhighenergycol-lisionshasremainedanopenissue.Anaiveinterpreta-tionoftheφenhancementobservedinheavy-ioncolli-sionswouldbethattheφKK

¯isproducedhadronicallyvia→φ.

HadronicrescatteringmodelssuchasRQMDandUrQMD[11,12],implementingsuchprocesses,pre-dictanincreaseintheφ/K ratioasafunctionofthenumberofparticipants.Rescatteringmodelsalsopredictsimilarincreasesinthe ptThenuclearmodi cation offactorstheproton(RAAandandφRmeson.CP)oftheφmesonareimportantindi erentiatingbetweenmassandparticlespeciesordering.Currentmeasure-mentsofidenti edhadronsbySTAR(ΛandK0

thatRCPfortheΛdi ersfromthatoftheK0

S)show

todeterminewhetherthisS[13].Itisdi cult,however,di erenceisrelatedtothemassoftheparticleorthetypeoftheparticle(whetheritisabaryonorameson)sincethereasigni cantmassdi erencebetweentheΛandtheK,however,hasamassthatissimilartothatoftheS0

is

.TheφΛ,yetisameson.AdirectcomparisonoftheφRCPandRAAwiththesepreviousmeasurementswillprovidemoreinsightintothismassvs.particlespeciesdependence.TheSTARdetector[14]consistsofseveralsub-systemsinalargesolenoidalanalyzingmagnet.ForthedatatakenduringthesecondRHICrun(2001-2002)presentedhere,theexperimentalsetupconsistedofaTimeProjec-tionChamber(TPC),aCentralTriggerBarrel(CTB),apairofBeam-BeamCounters(BBC),andtwoZeroDe-greeCalorimeters(ZDC).TheZDC’sareusedastheex-perimentaltriggerforAu+AucollisionswhiletheBBC’sareusedforthep+ptrigger.

Theresultspresentedherewereobtainedfromabout2.1millionminimum-biasAu+Auevents,1.1millioncen-tralAu+Aueventsand6.5millionnon-singly-di ractive(NSD)p+pevents.Reconstructionoftheφwasaccom-plishedbycalculatingtheinvariantmass(minv),trans-versemomentum(pt),andrapidity(y)ofpairsthatformedfromallpermutationsofcandidateK+withK .Theresultingminvdistributionconsistedoftheφsignalatopalargebackgroundthatispredominantlycombina-torial.Theshapeofthecombinatorialbackgroundwascalculatedusingthemixed-eventtechnique[15,16].Forthecentralitymeasurement,therawhadronmul-tiplicitydistributionwithinapseudo-rapiditywindow|80%,η|≤30-50%,0.5isdivided10–30%,intotop ve10%binsandcorrespondingtop5%ofthetomea-50–suredcrosssectionforAu+Aucollisions.EventsareselectedwithaprimaryvertexzpositionfromthecenteroftheTPCof|z|<25cmforAu+Aucollisionsand|beamz|<axis.50cmTheseforpevents+pcollisions,arefurther …… 此处隐藏：15521字，全部文档内容请下载后查看。喜欢就下载吧 ……