Screening of mass singularities and finite soft-photon production rate in hot QCD

TL;DR

This paper calculates the soft photon production rate in hot QCD, addressing mass singularities with a resummed effective propagator, and finds that damping rates are crucial for screening divergences.

Contribution

It introduces a self-consistent resummation method using an effective hard-quark propagator to screen mass singularities in photon production rates.

Findings

Mass singularities are screened by damping-rate effects.

Effective propagator resummation improves divergence handling.

Photon-quark vertex corrections contribute significantly.

Abstract

The production rate of a soft photon from a hot quark-gluon plasma is computed to leading order at logarithmic accuracy. The canonical hard-thermal-loop resummation scheme leads to logarithmically divergent production rate due to mass singularities. We show that these mass singularities are screened by employing the effective hard-quark propagator, which is obtained through resummation of one-loop self-energy part in a self-consistent manner. The damping-rate part of the effective hard-quark propagator, rather than the thermal-mass part, plays the dominant role of screening mass singularities. Diagrams including photon--(hard-)quark vertex corrections also yield leading contribution to the production rate.