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

TL;DR

This paper investigates how variations in thermal quark mass and running coupling influence photon emission in heavy-ion collisions, showing that certain assumptions can explain about half of the observed photon spectrum.

Contribution

It introduces a detailed analysis of collinear photon emission considering thermal quark mass variations, aligning theoretical predictions with experimental data.

Findings

Lower thermal quark mass (~50-100 MeV) explains ~50% of photon spectrum at 2-3 GeV.

Higher quark mass (~300 MeV) underestimates experimental photon yields.

Collinear processes significantly contribute to photon production in quark-gluon plasma.

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.