Modified Fragmentation Function in Heavy Ion Collisions at RHIC via Direct photon-Jet Measurements - Nuclear Experiment

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Abstract: The presented results are the first measurements at RHIC for direct$\gamma$-charged hadron azimuthal correlations in heavy ion collisions. We usethese correlations to study the color charge density of the medium through themedium-induced modification of high-p$T$ parton fragmentation. Azimuthalcorrelations of direct photons at high transverse energy 8 $<$ p$T$ $<$ 16GeV with away-side charged hadrons of transverse momentum 3 $<$ p$T$ $<$ 6GeV-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 STARexperiment. A transverse shower shape analysis in the STAR BarrelElectromagnetic Calorimeter Shower Maximum Detector is used to discriminatebetween the direct photons and photons from the decays of high p$T$ $\pi^{0}$.The per-trigger away-side yield of direct $\gamma$ is smaller than from$\pi^{0}$ trigger at the same centrality class. Within the current uncertaintythe I${CP}$ of direct $\gamma$ and $\pi^{0}$ are similar.

Autor: Ahmed M. Hamed

Fuente: https://arxiv.org/