Direct photon-hadron correlation measurement and a way towards photon-triggered jets at RHIC

Abstract

We report the results of $\gamma_{\rm dir}$ and $\pi^{0}$-hadron azimuthal correlations as a measure of the away-side jet-like correlated yields in central Au+Au and p+p collisions at $\sqrt{s_{_{NN}}}$=200 GeV in the STAR experiment. The charged-hadron per-trigger yields at mid-rapidity with respect to high-$p_{T}$ $\gamma_{\rm dir}$ and $\pi^{0}$ in central Au+Au collisions are compared with p+p collisions. Within uncertainties, the same $z_{T}$ (~$p_{T}^{\mathrm{assoc}}$ / $p_{T}^{\mathrm{trig}}$) dependence of the suppression is observed for $\gamma_{\rm dir}$ and $\pi^{0}$ - triggers. The results are compared with energy-loss model predictions. The $\gamma-\rm jet$ measurements can provide further understanding on the redistribution of in-medium energy loss. Ongoing $\gamma-\rm jet$ studies in the STAR experiment are also discussed.