Rapidity distribution of photons from an anisotropic quark-gluon plasma

Abstract

We calculate rapidity distribution of photons due to Compton and annihilation processes from quark gluon plasma with pre-equilibrium momentum-space anisotropy. We also include contributions from hadronic matter with late-stage transverse expansion. A phenomenological model has been used for the time evolution of hard momentum scale, ${p}_{\mathrm{hard}}(\ensuremath{\tau})$, and anisotropy parameter, $\ensuremath{\xi}(\ensuremath{\tau})$. As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of photons rapidity distribution. For example, with the fixed initial condition (FIC) free-streaming ($\ensuremath{\delta}=2$) interpolating model we observe significant enhancement of photon rapidity distribution at fixed ${p}_{T}$, where as for FIC collisionally broadened ($\ensuremath{\delta}=2/3$) interpolating model the yield increases till $y~1$. Beyond that suppression is observed. With fixed final multiplicity (FFM) free-streaming interpolating model we predict enhancement of photon yield which is less than the case of FIC. Suppression is always observed for FFM collisionally broadened interpolating model.