KLN theorem, magnetic mass, and thermal photon production

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.

9 pages Latex document, 5 postscript figures, modified figure 5 and slightly updated section 3