A Ramsey Neutron-Beam Experiment to Search for Ultralight Axion Dark Matter at the ESS

TL;DR

This paper proposes a novel neutron-beam Ramsey experiment at the ESS to detect ultralight axion dark matter by observing neutron spin rotations, potentially surpassing current sensitivity limits by 2-3 orders of magnitude.

Contribution

It introduces a new experimental approach using high-intensity neutron beams to significantly improve sensitivity to axion-neutron coupling in the ultralight mass range.

Findings

Potential to improve sensitivity by 2-3 orders of magnitude

Applicable to axion mass range $10^{-22}$ to $10^{-16}$ eV

Feasible at the HIBEAM beamline at the ESS

Abstract

High-intensity neutron beams, such as those available at the European Spallation Source (ESS), provide new opportunities for fundamental discoveries. Here we discuss a novel Ramsey neutron-beam experiment to search for ultralight axion dark matter through its coupling to neutron spins, which would cause the neutron spins to rotate about the velocity of the neutrons relative to the dark matter halo. We estimate that experiments at the HIBEAM beamline at the ESS can improve the sensitivity to the axion-neutron coupling compared to the current best laboratory limits by up to $2-3$ orders of magnitude over the axion mass range $10^{-22} \, \textrm{eV} - 10^{-16}$ eV.