Beam-Energy and Centrality Dependence of Directed Flow of ...Prashanth Shanmuganathan Thesis...
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Beam-Energy and Centrality Dependence of Directed Flow of Identified Particles Prashanth Shanmuganathan Thesis Advisor: Prof. Declan Keane Kent State University, Ohio
Transcript of Beam-Energy and Centrality Dependence of Directed Flow of ...Prashanth Shanmuganathan Thesis...
Beam-EnergyandCentralityDependenceofDirectedFlowof
IdentifiedParticlesPrashanthShanmuganathan
ThesisAdvisor:Prof.DeclanKeaneKentStateUniversity,Ohio
BESProgramatSTARandDirectedFlowGoalsofBES:ExploreQCDphasediagram• Mapturn-offofQGPsignatures• SearchforaCriticalPoint• SearchforaFirst-OrderPhaseTransition
√sNN(GeV) 7.7 11.5 14.5 19.6 27 39Events (106)Minimum-bias 4 12 20 36 70 130
Data:Au+Aucollisions
• Hydrowiththe1st-orderphasetransitionshowsdipindirectedflowvs.beamenergyduetosuddensofteningofEOS
• Protonv1 probesinterplayofbaryontransportandhydrobehavior
• Protondv1/dy vs.beamenergychangessign,withaminimum.
• EOSsoftening?
• NewΛ dataoffermoreinsightintotransportofbaryonsPRL112,162301(2014) 2
STAR&ParticleIdentificationdE
/dx(keV/cm
) TPCp
K+π+
p(GeV/c)
√SNN=39GeV TOF
π+K+
p
p(GeV/c)
mass2(GeV
/c2 )2 √SNN=39GeV
• Uniform&LargeAcceptance• Fullazimuthalcoverage• |η|<1coverage M.&A.Schmah
• PID usingenergylossinTPC dE/dx
• PID usingtimeofflightandmomentumfromTPC
Long-lived:p,K,π• RequiresTPC&TOFhits• dE/dx cutofnσ ≤2• p :0.4< pT < 2.0GeV/c• K± &π± :pT >0.2GeV/c• p <1.6GeV/cShort-lived:Λ&K0
S• Invariantmasstechnique• Mixed-eventbackground• V0 topologicalcuts• TPCand/orToFhitsfor
daughters• 0.2< pT <5.0GeV/c
InvariantmassofLambda(11.5GeV)
TOF
TPCBBC
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preliminary preliminary
preliminary
EventPlaneEstimation• 1st-orderreactionplaneestimatedusingEast&WestBBCdetectors–Coverage:3.3<|η|<5.0–η gapbetweenTPC andBBCreducesnon-flow
• BBCeventplaneresolutionimprovesatlowerenergiesduetostrongv1signalnearbeamrapidities aligningwithBBCacceptance
• Non-flatBBCΨ1 distributioncorrectedbyshiftingmethod(Voloshin,Poskanzer,Snellings,arXiv:0809.2949)
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v1 vs.rapidity for10-40%centrality
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dv1/dy vs.BeamEnergyfor10-40%centrality
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preliminary • Alinearfitover|y|≤0.8usedtofinddv1/dy forallspecies&energies
• Λ followsp withinerrors
• Anti-pandanti-Λ havenegativeslopeforallBESenergies
• Chargedpions havenegativeslopeforallBESenergies
80-7
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dv1/dyvs.centralityforπ±,p,Λ
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preliminaryΛp π+
Summary•Wepresentv1(y)andmidrapidity dv1/dy at7.7,11.5,14.5,19.6,27and39GeVinAu+Au collisions forp, anti-p,Λ,anti-Λ,K±,K0,π±,at9centralities
• dv1/dy|y=0 forbothp,Λ showssignchangeandstronglydependsonbeamenergyandcollisioncentrality
• Therearedistinctqualitativefeaturesin10-40%centralitydv1/dy forbaryons(signchange&minimum),antibaryons(alwaysnegative),mesons(negative&smallermagnitude)
•Modelswithandwithoutphasetransitionsdon’treproducenotablequalitativefeaturesofdata(especiallyp,Λ)
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