Constraints on axion-like dark matter from a SERF comagnetometer

TL;DR

This paper reports terrestrial bounds on axion-like dark matter coupling to neutrons and protons using a SERF comagnetometer, covering a specific mass range and improving previous constraints significantly.

Contribution

First terrestrial bounds on axion-like dark matter coupling to protons, using a SERF comagnetometer, covering an unexplored parameter space.

Findings

Bounds surpass astrophysical limits for certain masses.

First terrestrial constraints on proton coupling with axion-like dark matter.

Improved constraints over previous terrestrial experiments by over two orders of magnitude.

Abstract

Ultralight axion-like particles are well-motivated relics that might compose the cosmological dark matter and source anomalous time-dependent magnetic fields. We report on terrestrial bounds from the Noble And Alkali Spin Detectors for Ultralight Coherent darK matter (NASDUCK) collaboration on the coupling of axion-like particles to neutrons and protons. The detector uses nuclei of noble-gas and alkali-metal atoms and operates in the Spin-Exchange Relaxation-Free~(SERF) regime, achieving high sensitivity to axion-like dark matter fields. Conducting a month-long search, we cover the mass range of $1.4\times 10^{-12}$~eV/$c^2$ to $2\times 10^{-10}$~eV/$c^2$ and provide limits which supersede robust astrophysical bounds, and improve upon previous terrestrial constraints by over two orders of magnitude for many masses within this range for protons, and up to two orders of magnitude for neutrons. These are the first reliable terrestrial bounds reported on the coupling of protons with axion-like dark matter, covering an unexplored terrain in its parameter space.