Detecting the Coupling of Axion Dark Matter to Neutron Spins at Spallation Sources via Rabi Oscillation

Abstract

We propose a novel detection method for axion dark matter using the Rabi oscillation of neutron spins in beam-based measurements. If axions couple to neutron spins, a background oscillating axion dark matter field would drive transitions between spin-up and spin-down neutron states in a magnetic field when the axion particle energy matches the energy gap between the spin states. The transition can be detected in a double-Stern-Gerlach-type apparatus, with the first splitter producing a pure spin-polarized neutron beam and the second splitter selecting spin-flipped signals. Our approach offers enhanced detection capability for axions within the $10^{-12}-10^{-10}$eV mass window with the capability to surpass the sensitivity of current laboratory experiments.

7 pages, 2 figures. References added