Azimuthal anisotropy measurement of direct photon in √s NN =200GeV Au+Au collisions at RHIC-PHENIX Photons should be emitted from several states such as the initial state, QGP state, and the hadron-gas state. We define the direct photons as all remaining photons after subtraction of all hadron decay photons, the main back ground for the direct photon analysis.. We attempt to measure the azimuthal anisotropy measure- ment of direct photons in √s NN =20 0GeV Au+Au collisions.. If this direct photon v 2 is measured 1. Abstract 00   prompt photon thermal photon jet fragment photon hadron decay photon PHENIX preliminary 2. Direct photon 4. methods 5. Results Univ. of Tsukuba Kentaro Miki for the PHENIX collaboration with enough accuracy, it offers the ability to distinguish thermal from other photon sources and thereby present more reliable evidence of the QGP. In this presentation, we will show the current status of the direct photon v 2 analysis at RHIC- PHENIX.. Direct photons are one of the most effective probes to study properties of hot dense medium at initial state of heavy ion collisions be- cause photons have much weaker interactions with other particles and thus preserve information about their creation.. Quark Matter 2006 Shanghai - China Nov. 14 – 20, 2006 The prompt photon is generated by pQCD process at parton-parton scattering in early stage and emitted to random direction. So we can expect that the prompt photon v 2 is equal to 0.. The thermal photon v 2 which is emitted from hot-dense matter, is expected to positive because it’s reflected the expansion direction and surface size of source.. prompt photon v 2 = 0 thermal photon v 2 > 0 We estimated the direct photon v 2 in √s NN =200GeV Au+Au collisions at RHIC-PHENIX by subtracted hadron decay photon from inclusive photon v 2.. The second harmonic coefficient parameter v 2 of the azimuthal distribution of the particles produced in heavy ion collisions is defined by following function.  : azimuthal direction of the particles  RP : direction of the reaction plane In this analysis, the Electro-Magnetic Calorimeter (EMCal) was used for measuring the energy of photons.. The analysis of direct photons require determining background photons decaying from known hadronic sources such as  0 and . The  0 distribution are determined by invariant mass analysis of photon pairs, with combinatorial background subtraction. invariant mass distribution of  0 Energy cut (Ecore > 0.2 GeV) shower shape cut (  2 < 3) EMCal TOF cut (TOF < 1.2 ns) charged VETO cut (pc3hit > 6.5 cm) Au + Au √s NN =200 GeV PHENIX preliminary Au + Au √s NN =200 GeV  inclusive /  back ground The amount of direct photon yield increases in a high area. 3. Direct photon v 2 is equal to zero ? or not ? thermal window -> 1~3 GeV/c (?) jet – thermal window -> 3~5 GeV/c (?) prompt photon -> 6~ GeV/c (?) annihilation compton scattering Bremsstrahlung (energy loss) jet jet fragment photon v 2 > 0 v 2 < 0 1.0~3.03.0~5.05.0~10.0 combinatorial back ground was subtract- ed from invariant mass distribution at each centrality,  and p T..  0 candidate was defined by counting its entry, and filled each centrality and p T bins as function of . And then, v 2 was estimated by fitting these distribution.. Invariant mass distribution of  0 after subtracted combinatrial BG. dN / d  distribution at each p T bins. PHENIX detector (central arm) S. Turbide et al. PRC 69(2004) Finally, we present the direct photon v 2 as a function of p T at 20 % centrality step. The direct photon v 2 near 3~4 GeV/c, seems to have positive v 2. And in high p T, the v 2 is equal to zero within error bar. Additionally, the direct photon v 2 seems to have centrality dependence.. Result of this analysis still have too large error. Then, we should attempt to reduce the error used by another analysis method (conversion method or etc…) or increased the statistics. By doing so, we expect this v 2 becomes powerful analysis to thermal photon analysis.. Rupa Chatterjee et al. PRL (2006) theoretical curves of thermal photon