Bremsstrahlung and photon production in thermal QCD

In this paper, we extend the study of bremsstrahlung photon production in a quark-gluon plasma to the cases of soft static photons (q = 0) and hard real photons. The general framework of this study is the effective perturbative expansion based on the resummation of hard thermal loops. Despite the fact that brensstrahlung only comes at two loops, we find that in both cases, it generates contributions of the same order of magnitude as those already calculated by several other groups at one loop. Furthermore, a new process contained in the two-loop diagrams dominates the emission of a very hard real photon. In all cases, the rate of real or virtual photon production in the plasma is appreciably increased compared to the one-loop predictions. [S0556-2821(98)01418-0].