Bremsstrahlung from an equilibrating quark-gluon plasma - art. no. 014902

The photon production rate from a chemically;equilibrating quark-gluon plas ma likely to be produced at RHIC (BNL) and LHC (CERN) energies is estimated taking into account bremsstrahlung. The plasma is assumed to be in local t hermal equilibrium, but with a phase space distribution that deviates from the Fermi or Bose distribution by space-time dependent factors (fugacities) . The photon spectrum is obtained by integrating the photon rate over the s pace-time history of the plasma, adopting a boost invariant cylindrically s ymmetric transverse expansion of the system with different nuclear profile functions. Initial conditions obtained from a self-screened parton cascade calculation and, for comparison, from the HIJING model are used. Compared t o an equilibrated plasma at the same initial energy density, taken from the self-screened parton cascade, a moderate suppression of the photon yield b y a factor of 1 to 5 depending on the collision energy and the photon momen tum is observed. The individual contributions to the photon production, how ever, are completely different in the both scenarios.