In this paper, we extend the study of bremsstrahlung photon production in a quark-gluon plasma to the cases of soft static photons 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 bremsstrahlung 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 dominate 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.Comment: 35 pages, LaTeX2e, uses class article and package graphics, 13 postscript figure

In the light of the new prompt photon data collected by PHENIX at RHIC and by D∅ at the run II of the Tevatron, we revisit the world prompt photon data, both inclusive and isolated, in hadronic collisions, and compare them with the NLO QCD calculations implemented in the Monte Carlo programme JETPHOX.

In this paper, we derive a simple sum rule satisfied by the gluon spectral function at finite temperature. This sum rule is useful in order to calculate exactly some integrals that appear frequently in the photon or dilepton production rate by a quark gluon plasma. Using this sum rule, we rederive simply some known results and obtain some new results that would be extremely difficult to justify otherwise. In particular, we derive an exact expression for the collision integral that appears in the calculation of the Landau-Pomeranchuk-Migdal effect. LAPTH-909/02, LPT-ORSAY-02/272 The term in M 2 ∞ K T ,L was forgotten in [26]. It comes from the HTL correction to the γqq vertex. This vertex correction was also neglected in [32,33], without any damage to this approach since it affects only the component Πzz of the polarization tensor, while only the transverse components are calculated in these papers (see [37] for more details on this issue).3 Some very partial asymptotic results have been obtained in [26] for J T ,L . 4A Asymptotic behavior of F (x)