Non-thermal photons from the pre-equilibrium stages

Abstract

I compute the invariant yield of photons from the pre-equilibrium stage of heavy-ion collision using the ”bottom-up” thermalization scenario and scaling gluon distributions found in classical statistical lattice simulations. I find it to dominate the spectrum specially at higher values of the saturation scale . I constrain the system using charge hadron multiplicities from LHC and RHIC, where fair agreement with data is obtained. Finally, I present a comparison of the ”bottom-up” scenario to one in which a thermal stage is achieved at an early time, Qsτ ∼ 1.