Se p 20 08 Photons from anisotropic Quark - Gluon - Plasma

We calculate medium photons due to Compton and annihilation processes in an anisotropic media. The effects of time-dependent momentum-space anisotropy of Quark-Gluon-Plasma (QGP) on the medium photon production are discussed. Such an anisotropy can results from the initial rapid longitudinal expansion of the matter, created in relativistic heavy ion collisions. A phenomenological model for the time-dependence of the parton hard momentum scale, phard(τ), and anisotropy parameter, ξ(τ), has been used to describe the plasma space-time evolution. We find significant dependency of photon yield on the isotropization time (τiso). It is shown that the introduction of early time momentum-space anisotropy can enhance the photon production by a factor of 10 (1.5) (in the central rapidity region) for free streaming (collisionally-broadened) interpolating model if we assume fixed initial condition. On the other hand, enforcing the fixed final multiplicity significantly reduces the enhancement of medium photon production.