Comment on "Hadronic production of thermal photons"

Recently Turbide 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-channel omega-exchange process in the pi rho ->pi 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 omega meson exchange processes. We have evaluated the photon emission rate from the process pi rho -> a(1)->pi 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 omega and a(1) exchange processes in photon production.