Polarized Photons from the Early Stages of Relativistic Heavy-Ion Collisions

The polarization of real photons emitted from early-time heavy-ion collisions is calculated, concentrating on the contribution from bremsstrahlung and quark-antiquark annihilation processes at leading order in the strong coupling. The effect of an initial momentum space anisotropy of the parton distribution is evaluated using a model for the non-equilibrium scattering kernel for momentum broadening. The effect on the photon polarization is reported for different degrees of anisotropy. The real photons emitted early during in-medium interactions will be dominantly polarized along the beam axis.