Shedding Light on Dark Matter: A Faraday Rotation Experiment to Limit a Dark Magnetic Moment

TL;DR

This paper proposes a Faraday rotation experiment to constrain the magnetic moment of dark matter particles, especially at keV masses, by analyzing how such particles could influence electromagnetic polarization.

Contribution

It introduces a novel experimental approach to limit dark matter magnetic moments across a range of masses, emphasizing the potential at keV scales.

Findings

Limits on dark matter magnetic moments increase as particle mass decreases.

Most stringent constraints are at the keV mass scale for thermal relics.

Experimental feasibility for measuring these effects is discussed.

Abstract

A Faraday rotation experiment can set limits on the magnetic moment of a electrically-neutral, dark-matter particle, and the limits increase in stringency as the candidate-particle mass decreases. Consequently, if we assume the dark-matter particle to be a thermal relic, our most stringent constraints emerge at the keV mass scale. We discuss how such an experiment could be realized and determine the limits on the magnetic moment as a function of mass which follow given demonstrated experimental capacities.