Abstract
Axion-like particles are promising candidates to make up the dark matter of the universe, but it is challenging to design experiments that can detect them over their entire allowed mass range. Dark matter in general, and in particular axion-like particles and hidden photons, can be as light as roughly $10^{-22} \;\rm{eV}$ ($\sim 10^{-8} \;\rm{Hz}$), with astrophysical anomalies providing motivation for the lightest masses ("fuzzy dark matter"). We propose experimental techniques for direct detection of axion-like dark matter in the mass range from roughly $10^{-13} \;\rm{eV}$ ($\sim 10^2 \;\rm{Hz}$) down to the lowest possible masses. In this range, these axion-like particles act as a time-oscillating magnetic field coupling only to spin, inducing effects such as a time-oscillating torque and periodic variations in the spin-precession frequency with the frequency and direction set by fundamental physics. We show how these signals can be measured using existing experimental technology, including torsion pendulums, atomic magnetometers, and atom interferometry. These experiments demonstrate a strong discovery capability, with future iterations of these experiments capable of pushing several orders of magnitude past current astrophysical bounds.
Highlights
The cold-dark-matter paradigm has been established as a critical part of our understanding of cosmology, but the fundamental nature of this dark matter remains unknown [1]
We present several experiments that can be modified or created to search for axions at the lightest masses, and evaluate their potential to reach axion couplings several orders of magnitude beyond current astrophysical bounds
We focus exclusively on axionlike particles, and focus on Published by the American Physical Society the nature and potential discovery of ultralight dark matter composed primarily of these particles
Summary
The cold-dark-matter paradigm has been established as a critical part of our understanding of cosmology, but the fundamental nature of this dark matter remains unknown [1]. We can immediately see a correspondencpeffibffiffiffieffiffitffiwffiffiffieen this energy shift bψ and the axion coupling gaψψ v 2ρDM, so we expect the LIV signal to be identical to the axion signal in the zero axion mass limit These same experiments, including spin-polarized torsion pendulums and atomic magnetometers, can be used with little to no modification to search for slowly varying axion fields. We study the experimental effects of axionlike particles at the lowest axion masses, i.e. ma ∼ 10−14–10−22 eV, including the mass range of fuzzy dark matter. It is interesting to note that a nucleon spin precession measurement for dark matter has recently been performed [28], which, it does not reach beyond the astrophysics bounds, does present the first dedicated analysis for this type of coupling in this mass range. VI with a discussion of the landscape for new experiments designed to detect axions
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