Adiabatic Conversion of ALPs into Dark Photon Dark Matter

TL;DR

This paper proposes a new mechanism where misaligned axion-like particles (ALPs) convert into dark photon dark matter via background magnetic fields, potentially explaining dark matter abundance across a wide mass range.

Contribution

It introduces a novel conversion mechanism from ALPs to dark photons in a homogeneous magnetic field, enabling dark matter production without momentum redshifting.

Findings

Can produce non-relativistic dark photons from ALPs

Reproduces dark matter relic abundance for masses down to 10^{-13} eV

Applicable with magnetic fields from early universe phase transitions

Abstract

We introduce a mechanism by which a misaligned ALP can be dynamically converted into a dark photon in the presence of a background magnetic field. An abundance of non-relativistic ALPs will convert to dark photons with momentum of order the inhomogeneities in the background field; therefore a highly homogeneous field will produce non-relativistic dark photons without relying on any redshifting of their momenta. Taking hidden sector magnetic fields produced by a first order phase transition, the mechanism can reproduce the relic abundance of dark matter for a wide range of dark photon masses down to $10^{-13}$ eV.