Abstract
The presented results are the first measurements at RHIC for direct γ-charged hadron azimuthal correlations in heavy ion collisions. We use these correlations to study the color charge density of the medium through the medium-induced modification of high-p T parton fragmentation. Azimuthal correlations of direct photons at high transverse energy (8<p T <16 GeV) with away-side charged hadrons of transverse momentum (3<p T <6 GeV/c) have been measured over a broad range of centrality for Au+Au collisions and p+p collisions at \(\sqrt{s_{NN}}=200\) GeV in the STAR experiment. A transverse shower shape analysis in the STAR Barrel Electromagnetic Calorimeter Shower Maximum Detector is used to discriminate between the direct photons and photons from the decays of high p T π 0. The per-trigger away-side yield of direct γ is smaller than from π 0 trigger at the same centrality class. Within the current uncertainty the I CP of direct γ and π 0 are similar.
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Hamed, A.M. Modified fragmentation function in heavy ion collisions at RHIC via direct γ-jet measurements. Eur. Phys. J. C 61, 597–601 (2009). https://doi.org/10.1140/epjc/s10052-009-0960-z
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DOI: https://doi.org/10.1140/epjc/s10052-009-0960-z