1. Why 1 What 2 How 3 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
direct photon
photon from jet is …
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 ??
|| < =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 ? p K e g m
Space (z)
Time A
K0* f　W　
Jets
0.6fm/c
4fm/c
16fm/c
8fm/c
hadron gas　
equilibrated QGP　
thermalization
inclusive photon
R=Ninc / N BG
00 to 92 %
work in progress
direct photon
mixed　phase　
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