Azimuthal elliptic anisotropy ($v_{{}_2}$) of high-$p_{{}_T}$ direct $\gamma$ in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV

Abstract

Preliminary results from the STAR collaboration for the azimuthal elliptic anisotropy $(v_{{}_2})$ of high transverse momentum ($p_{{}_T}$) direct photons (${\gamma }_{{}_{dir}}$) produced at mid-rapidity ($|{\eta }^{{\gamma }_{{}_{dir}}}|<1$) in Au+Au collisions at center-of-mass energy $\sqrt{s_{{}_{NN}}}=200$~GeV are presented, and compared to the measured $(v_{{}_2})$ of neutral pions (${\pi }^0$) in the same kinematic range. The electromagnetic transverse shower profile is used to distinguish ${\pi }^0$ from direct photons. The measured $v_{{}_2}^{{\gamma }_{{}_{dir}}}(p_{{}_T})$ at high $p_{{}_T}$ ($8<p_{{}_T}^{{\gamma }_{{}_{dir}}}<20$~GeV/$c$) is found to be smaller than that of ${\pi }^0$ and consistent with zero when using the forward detectors in determining the event plane.

arXiv comment9th International Workshop on High-pT Physics at LHC. arXiv admin note: substantial text overlap with arXiv:1008.4894

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