Virtual-photon bremsstrahlung in a quark-gluon plasma

The production of dielectron pairs due to bremsstrahlung of quarks is calculated in a hot quark-gluon plasma. It is shown that multiple scattering of quarks leads to an infrared stable result for dielectron emission rates. The influence of the Landau-Pomeranchuk effect, due to destructive interference of virtual photons, is calculated and analyzed. For the soft electromagnetic signal from a QCD plasma, this effect is more important than the one due to the thermal quark mass; it furthermore reduces significantly the dielectron production rates. It is also shown that in the low invariant-mass region the contributions from quark and pion virtual bremsstrahlung are of the same order of magnitude.