Photons from anisotropic Quark-Gluon-Plasma

Abstract

We calculate medium photons due to Compton and annihilation processes in an anisotropic media. The effects of time-dependent momentum-space anisotropy of {\em 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, $p_{hard}(\tau )$, and anisotropy parameter, $\xi (\tau )$, has been used to describe the plasma space-time evolution. We find significant dependency of photon yield on the isotropization time (${\tau }_{iso}$). 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 {\em free streaming} ({\em collisionally-broadened}) {\em 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.

Comments: 15 pages, 19 figures, few refs added, one new paragraph is added in introduction, published in Physical Rev. C