| Abstract: |
Axions are well-motivated particles from both the top-down and bottom-up perspectives, and so they constitute promising candidates for beyond the standard model physics. As such, there is an extensive experimental program searching for axions via their potential couplings to the Standard Model. A leading direction in the hunt for axion dark matter is to search for its influence on nuclear spins. In this talk, I will analyze the axion signal and background contributions that arise in such experiments (a prominent example being CASPEr). In the limit where the transverse spin-relaxation time of the material is the largest timescale of the problem, I will show that the induced signal continues to grow even beyond the coherence time of the axion field, which leads to key differences with the existing literature. As a result, I will show that spin-precession instruments are much more sensitive than what has been previously estimated in a sizable range of axion masses. This improves the detection prospects for the QCD axion, and I will estimate the experimental requirements to reach this motivated target. I will also describe how nuclear spin experiments can be utilized to search for a cosmic axion background signal and how such signals are motivated from the theoretical standpoint.
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