Dielectric haloscopes: sensitivity to the axion dark matter velocity

TL;DR

This paper investigates how the velocity of axion dark matter affects dielectric haloscopes, finding that for current setups velocity effects are negligible, but future experiments could measure axion velocities to gain astrophysical insights.

Contribution

It provides a detailed analysis of velocity effects in dielectric haloscopes and discusses implications for future directional axion detection experiments.

Findings

Velocity effects are negligible for the planned MADMAX setup.

Future experiments could be sensitive to axion velocity and direction.

Velocity dependence becomes significant when haloscope size exceeds 20% of the axion de Broglie wavelength.

Abstract

We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass ($40-400~\mu$eV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics.