Photons production from the early stages of relativistic heavy ion collisions

We present preliminary results about photons production in relativistic heavy ion collisions. The main novelty of our study is the calculation of the contribution of the pre-equilibrium stage to the photon spectrum. The initial stage is modeled by an ensemble of classical gluon fields which decay to a quark-gluon plasma via the Schwinger mechanism, and the evolution of the system is studied by coupling classical field equations to relativistic kinetic theory; photons production is then computed by adding collision processes into the collision integral. We find that the contribution of early stage photons to the direct photon spectrum is substantial in the transverse momentum region pT greater than or similar to 1.5 GeV.