Direct-photon+hadron correlations to study parton energy loss with the STAR experiment

Abstract

We report new results of ${\gamma }_{dir}$+hadron 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 from years 2011 and 2009 of data taking, respectively. The charged-hadron per-trigger yields at mid-rapidity $(|\eta |<1)$ and for transverse momenta $p_T^{assoc}>1.2$ ~GeV/$c$ associated with ${\gamma }_{dir}$~ and ${\pi }^0$~(for triggers $|\eta |<$0.9, 12 $<p_T^{trig}<$ 20 GeV/$c$) in central Au+Au collisions are compared with p+p collisions. The $z_T$ ($=\frac{p_T^{assoc}}{p_T^{trig}}$) dependence, now extending down to $z_T$=0.1, of the suppression of the away-side associated yields is presented. We observed that the suppression of away-side associated yields tends to vanish at lower \zT. The dependence of the suppression on both $p_T^{assoc}$ and $p_T^{trig}$ is also discussed. Finally, these results are compared with various model predictions.

Comments: Proceedings of the Quark Matter 2015 conference, 4 pages, 5 figures