Production ofγγpairs 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 $q\overline{q}\to \gamma \gamma$ 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 $\gamma \gamma$ pairs. We compare these results with previous estimates of $\gamma \gamma$ production rates. Finally, for the phenomenology of heavy-ion collisions we present the screened $\gamma \gamma$ emission spectra by taking into account the space-time history of these collisions.