Hunting for Axionlike Dark Matter by Searching for an Oscillating Neutron Electric Dipole Moment

TL;DR

This study searches for ultra-low-mass axion-like dark matter through neutron and mercury atom spin-precession measurements, setting new laboratory constraints on axion couplings and finding no evidence of dark matter within the tested mass range.

Contribution

It provides the first laboratory constraints on axion-gluon coupling and improves existing limits on axion-nucleon interactions for ultra-low-mass axion-like particles.

Findings

No signal consistent with dark matter was observed.

Set the first laboratory constraints on axion-gluon coupling, surpassing astrophysical limits.

Improved constraints on axion-nucleon coupling by up to a factor of 40.

Abstract

We report on a search for ultra-low-mass axion-like dark matter by analysing the ratio of the spin-precession frequencies of stored ultracold neutrons and $^{199}$Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range $10^{-24}~\textrm{eV} \le m_a \le 10^{-17}~\textrm{eV}$. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40. The results were initially presented in Phys. Rev. X 7, 041034, of which this proceeding is largely a summary.