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.
Categories: nucl-ex hep-ex hep-ph nucl-th