The pre-equilibrium stage of ultra-relativistic heavy ion collisions and its impact on photon production

Lucia Oliva (Catania University)

We model the initial stage of ultra-relativistic heavy-ion collisions by a color-electric field which decays to a quark-gluon plasma by the Schwinger effect. We simulate the space-time evolution of the fireball by coupling in a self-consistent way relativistic kinetic equations to field equations. Including the pertinent microscopic scattering processes in the Boltzmann equation, we describe photon emission from the quark-gluon plasma and investigate the effect of the pre-equilibrium dynamics on the photon spectrum. We find that the early stage produces abundantly photons, comparable in number with those emitted by the equilibrated quark-gluon plasma during its whole lifetime; hence, there is no dark age in relativistic heavy ion collisions.