Enhanced photon production from quark-gluon plasma: Finite-lifetime effect

Photon production from a thermalized quark-gluon plasma of finite lifetime is studied directly in real time with a nonequilibrium formulation that includes off-shell (energy nonconserving) effects. To lowest order we find that production of direct photons form a quark-gluon plasma of temperature T ~ 200 MeV and lifetime t ~ 10-20 fm/c is strongly enhanced by off-shell (anti)quark bremsstrahlung q(\bar{q})->q(\bar{q})\gamma. The yield from this nonequilibrium finite-lifetime effect dominates over those obtained from higher order equilibrium rate calculations in the range of energy E > 2 GeV and falls off with a power law for E >> T.