On the photon-pseudoscalar particle mixing in media and external fields

TL;DR

This paper provides exact solutions for photon-pseudoscalar mixing in media with magnetic fields, improving understanding of transition efficiencies and revealing new longitudinal electromagnetic states relevant for laboratory searches of axion-like particles.

Contribution

It offers the first exact solutions to the coupled equations of motion for photon-pseudoscalar mixing in arbitrary magnetic field orientations and media, refining previous approximate methods.

Findings

Derived exact transition efficiencies for photon-pseudoscalar conversion.

Identified the generation of longitudinal electromagnetic states in non-perpendicular propagation.

Corrected and generalized previous approximate solutions in the literature.

Abstract

In this work, I study the mixing of photons with pseudoscalar particles and vice-versa in the presence of an external magnetic field and a pseudoscalar field. I solve exactly for the first time in the literature the equations of motion of the electromagnetic field coupled with a pseudoscalar field in the presence of a constant magnetic field with arbitrary direction with respect to the direction of propagation of the fields in vacuum. In addition, I also solve exactly the equations of motion in a magnetized plasma/gas for perpendicular propagation with respect to the external magnetic field. By finding exact solutions to the equations of motion, I find exact expressions for the transition efficiencies of photons into pseudoscalar particles in different situations. The expressions of the transition efficiencies generalize and correct those previously found in the literature by using approximate WKB methods on solving the equations of motion. In the case when the direction of propagation of fields with respect to the external magnetic field is not perpendicular, a longitudinal state of the electromagnetic field is generated even in a magnetized vacuum. The appearance of the longitudinal electric field state could be used for laboratory searches of pseudoscalar particles such as the axion and/or axion-like particles.