Photon and Axion Splitting in an Inhomogeneous Magnetic Field

TL;DR

This paper demonstrates that in an inhomogeneous magnetic field, axions and photons can be split into their particle and antiparticle components, an effect observable at first order in axion-photon coupling, unlike previous second-order effects.

Contribution

It introduces a novel scattering effect where axions and photons are decomposed into particle and antiparticle components in an inhomogeneous magnetic field, highlighting a first-order observable.

Findings

Particles and antiparticles are preferentially scattered in different directions.

The effect is first order in axion-photon coupling, making it potentially more detectable.

The magnetic interaction is analogous to scalar QED with an external electric potential.

Abstract

The axion photon system in an external magnetic field, when the direction of propagation of axions and photons is orthogonal to the direction of the external magnetic field, displays a continuous axion-photon duality symmetry in the limit the axion mass is neglected. The conservation law that follow in this effective 2+1 dimensional theory from this symmetry is obtained. The magnetic field interaction is seen to be equivalent to first order to the interaction of a complex charged field with an external electric potential, where this ficticious "electric potential" is proportional to the external magnetic field. This allows one to solve for the scattering amplitudes using already known scalar QED results. From the scalar QED analog the axion and the photon are symmetric and antisymmetric combinations of particle and antiparticle. If one considers therefore scattering experiments in which the two spatial dimensions of the effective theory are involved non trivially, one observes that both particle and antiparticle components of photons and axions are preferentially scattered in different directions, thus producing the splitting or decomposition of the photon and axion into their particle and antiparticle components in an inhomogeneous magnetic field. This observable in principle effect is of first order in the axion photon coupling, unlike the "light shining through a wall phenomena ", which is second order.