PHOTON PRODUCTION FROM A QUARK-GLUON PLASMA

In-medium interactions of a particle in a hot plasma are considered in the framework of thermal held theory. The formalism to calculate gaug e-invariant rates for photon and dilepton production from the medium i s given. In the application to a QED plasma, astrophysical consequence s are pointed out. The photon production rate from strongly interactin g quarks in the quark-gluon plasma, which might be formed in ultrarela tivistic heavy ion collisions, is calculated in the previously unacces sible regime of photon energies of the order of the plasma temperature . For temperatures below the chiral phase transition, an effective fie ld theory incorporating dynamical chiral symmetry breaking is employed , and perturbative QCD at higher temperatures. A smooth transition bet ween both regions is obtained. The relevance to the soft photon proble m and to high energy heavy ion experiments is discussed.