Measurement of Direct photon v 2 in √ s NN =200GeV Au+Au collisions at RHIC-PHENIX

1. g K0* fW m Jets Time p p K e 16fm/c hadron gas 8fm/c 4fm/c equilibrated QGP 0.6fm/c thermalization Space (z) A A Measurement of Direct photon v2 in √sNN=200GeV Au+Au collisions at RHIC-PHENIX Why 1 Kentaro Miki for the PHENIX Collaboration thermal photon v2>0 Univ. of Tsukuba prompt photon v2=0 do we measure Direct photon ? hadron decay photon v2>0 inclusive photon photon from jet is … direct photon annihilation compton scattering negative v2 prompt photon thermal photon photon form jet fragmentation hadron decay positive v2 Bremsstrahlung (energy loss) lead scintillator (PbSc) ・energy resolution 2.1  8.1 %/ E1/2 [GeV] v2 of direct photon is positive ? negative? or 0 ?? || < 0.375 =902 lead glass (PbGl) ・energy resolution 0.76  5.95 %/ E1/2 [GeV] probe of initial state of collision photon What 2 the result of v2 analysis ? inclusive photon R=Ninc / N BG 00 to 92 % work in progress direct photon mixedphase hadron decay photon neutral hadron which have decay mode to photon (0,,…) How 3 do we measure Direct photon ? work in progress work in progress work in progress estimate the 0 v2 hadron decay simulation R=Ninc / N BG 40 to 60 % R=Ninc / N BG 20 to 40 % R=Ninc / N BG 00 to 20 % estimate the inclusive photon v2 direct photon v2 direct photon v2 is … almost zero within the range of error bars. -> prompt photon is most effective. Energy cut (Ecore >0.2 GeV) shower shape cut (2 < 3) direct photon v2 has … centrality dependence. -> but still need to reduce errors more. EMCal TOF ( TOF < 1.2 ns) charged veto ( pc3hit > 6.5 cm) If we can reduce these errors especially low pT region, estimation of thermal photon v2 becomes possible. 1.0~3.0 3.0~5.0 5.0~10.0