New Observables for Direct Detection of Axion Dark Matter

TL;DR

This paper introduces novel observable signals for direct detection of ultralight axion-like dark matter, focusing on oscillating nuclear and electron moments detectable via NMR, extending current experimental bounds.

Contribution

It proposes a new detection method based on measuring oscillating moments induced by axion-like particles, expanding the experimental parameter space beyond existing limits.

Findings

Current bounds on time-varying moments are improved.

NMR techniques can detect axion-induced spin precession.

Parameter space exceeds astrophysical constraints.

Abstract

We propose new signals for the direct detection of ultralight dark matter such as the axion. Axion or axion like particle (ALP) dark matter may be thought of as a background, classical field. We consider couplings for this field which give rise to observable effects including a nuclear electric dipole moment, and axial nucleon and electron moments. These moments oscillate rapidly with frequencies accessible in the laboratory, ~ kHz to GHz, given by the dark matter mass. Thus, in contrast to WIMP detection, instead of searching for the hard scattering of a single dark matter particle, we are searching for the coherent effects of the entire classical dark matter field. We calculate current bounds on such time varying moments and consider a technique utilizing NMR methods to search for the induced spin precession. The parameter space probed by these techniques is well beyond current astrophysical limits and significantly extends laboratory probes. Spin precession is one way to search for these ultralight particles, but there may well be many new types of experiments that can search for dark matter using such time-varying moments.