Production of γγ pairs in a hot quark-gluon plasma and shielding of the quark mass singularity

We study the thermal production of large-invariant-mass photon pairs emitted from a quark-gluon plasma at high temperature. To lowest order in perturbation theory the cross section for the annihilation process (q bar q→γγ) is known to lead to logarithmically divergent thermal production rates for massless quarks. We apply recently developed resummation methods of finite-temperature perturbation theory and show how screening effects on quarks in the plasma provide finite thermal rates for γγ pairs. We compare these results with previous estimates of γγ production rates. Finally, for the phenomenology of heavy-ion collisions we present the screened γγ emission spectra by taking into account the space-time history of these collisions