Effective ALP-Photon Coupling in External Magnetic Fields

Abstract

We presented a complete calculation of the one-loop fermionic correction to the effective coupling between axion-like particles (ALPs) and photons within a constant, homogeneous magnetic field of arbitrary strength. This interaction, responsible for the Primakoff effect, is central to detecting axion-like particles in astrophysical settings and terrestrial experiments like helioscopes and haloscopes. Accurately predicting the interaction rate requires accounting for quantum corrections. Our work tackles this by employing magnetically field-dressed fermion propagators derived using Schwinger's proper time method and a systematic Lorentz decomposition using the Ritus basis. We evaluate the triangle loop diagram exactly, and compare it to approximations on field strength under specific assumptions.