Comment on “Hadronic production of thermal photons”

Abstract

Recently Turbide et al. have performed an exhaustive work on thermal photon production from hadronic matter [Phys. Rev. C 69, 014903 (2004)]. One of the findings of their work is that the $t\text{\ensuremath{-}}$channel \ensuremath{\omega}-exchange process in the $\ensuremath{\pi}\ensuremath{\rho}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\gamma}$ reaction constitutes the single most dominant contribution for thermal photons with energies beyond 2 GeV. In the present calculation we found that the contribution from the intermediary ${a}_{1}$ is more than that from the \ensuremath{\omega} meson exchange processes. We have evaluated the photon emission rate from the process $\ensuremath{\pi}\ensuremath{\rho}\ensuremath{\rightarrow}{a}_{1}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\gamma}$ for various interaction Lagrangians available in the literature. The effects of vertex form factors have been neglected because the main focus here is to understand the relative importance of \ensuremath{\omega} and ${a}_{1}$ exchange processes in photon production.