KLN theorem, magnetic mass, and thermal photon production

TL;DR

This paper investigates how infrared singularities in photon production from a quark-gluon plasma relate to the magnetic mass of gluons, revealing non-perturbative effects despite KLN theorem cancellations.

Contribution

It demonstrates that photon production rates remain sensitive to magnetic mass effects, highlighting limitations of perturbative calculations in this context.

Findings

Infrared singularities are canceled by the KLN theorem.

Photon production rate depends on the magnetic mass of gluons.

Rate remains non-perturbative due to magnetic mass sensitivity.

Abstract

We study the infrared singularities associated to ultra-soft transverse gluons in the calculation of photon production by a quark-gluon plasma. Despite the fact that the KLN theorem works in this context and provides cancellations of infrared singularities, it does not prevent the production rate of low invariant mass dileptons to be sensitive to the magnetic mass of gluons and therefore the rate to be non perturbative.