Energy Loss of Leading Hadrons and Direct Photon production in Evolving Quark-Gluon Plasma
Abstract
We calculate the nuclear modification factor of neutral pions and the photon yield at high pT in central Au-Au collisions at RHIC (s=200 GeV) and Pb-Pb collisions at the LHC (s=5500 GeV). A leading-order accurate treatment of jet energy loss in the medium has been convolved with a physical description of the initial spatial distribution of jets and a (1+1) dimensional expansion. We reproduce the nuclear modification factor of pion RAA at RHIC, assuming an initial temperature Ti=370 MeV and a formation time τi=0.26 fm/c, corresponding to dN/dy=1260. The resulting suppression depends on the particle rapidity density dN/dy but weakly on the initial temperature. The jet energy loss treatment is also included in the calculation of high pT photons. Photons coming from primordial hard N-N scattering are the dominant contribution at RHIC for pT > 5 GeV, while at the LHC, the range 8<pT<14 GeV is dominated by jet-photon conversion in the plasma.
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