Virtual photon bremsstrahlung in a magnetized quark-gluon-plasma

Abstract

We investigate dilepton production via virtual quark bremsstrahlung in a hot, magnetized quark-gluon plasma (QGP), extending the Landau-Pomeranchuk-Migdal (LPM) framework to account for a background magnetic field and for Fermi-Dirac quark statistics. An external electromagnetic field drives the quark distribution out of equilibrium, and this off-equilibrium correction, obtained from the Boltzmann equation in the relaxation-time approximation, is in principle explicit in the electric and magnetic field strengths. We argue that this correction, being linear in the electric field, vanishes identically upon integration over the full dilepton solid angle and therefore does not contribute to the dilepton production rate (DPR). The leading magnetic-field signature in the rate instead enters entirely through the equilibrium sector: the medium density and Debye screening mass, computed from the Landau-level structure of the magnetized QGP, modifying the LPM suppression parameter. Working in the regime relevant to the hydrodynamic phase of heavy-ion collisions, we present the LPM-induced DPR for quark scatterers and establish, for the first time, a nonzero magnetic-field imprint on this observable through the LPM mechanism.