Speaker
Dr
Nihar Sahoo
(Texas A & M University)
Description
Photons are valuable probes of the QCD plasma due to their lack of
color and electric charge. Direct photons ($\gamma_{dir}$), those
produced during the collision rather than from decays of hadrons, are not affected by the medium.The study of direct-photon-triggered away-side jets can give information about the energy loss of the away-side parton while
traversing through the medium. On the other hand, comparison between the suppression of $\gamma_{dir}$- and $\pi^{0}$- triggered away-side hadron yields can give information about the path-length and color-factor dependence of parton energy loss.
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. With this new low $p_{T}^{assoc}$ cut, we see evidence for the recovery of the lost energy in the low-momentum range for the constituents of the jet.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. 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.
| On behalf of collaboration: | STAR |
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Primary author
Dr
Nihar Sahoo
(Texas A & M University)
