Phenomenology of collinear photon emission from quark-gluon plasma in $AA$ collisions

Abstract

We study the role of running coupling and the effect of variation of the thermal quark mass on contribution of the collinear bremsstrahlung and annihilation to photon emission in $AA$ collisions in a scheme similar to that used in our previous jet quenching analyses. We find that for a scenario with the thermal quark mass $m_q\sim 50-100$ MeV contribution of the higher order collinear processes summed with the $2\to 2$ processes can explain a considerable part ($\sim 50$\%) of the experimental photon spectrum at $k_T\sim 2-3$ GeV for Au+Au collisions at $\sqrt{s}=0.2$ TeV. But for $m_q=300$ MeV and for the thermal quark mass predicted by the HTL scheme the theoretical predictions underestimate considerably the experimental spectrum.