Abstract:
While the possible interactions of dark matter (DM) with nucleons, electrons, and photons has been extensively studied, we propose extending the search for dark matter by considering its interactions with muons. In particular, an ultralight DM background may apply an oscillating torque to muon spins, causing them to follow novel precession trajectories. A time-resolved analysis of muon precession data from the upcoming Fermilab and J-PARC g-2 experiments is sensitive to this signal.
In addition, some DM candidates yield conventional precession with a shifted precession frequency, i.e. they make an apparent contribution to the anomalous muon magnetic dipole moment which depends on the local DM density. This allows immediate constraints to be placed on DM-muon interactions using the existing BNL g-2 measurement. Intriguingly, we also find that the muon g-2 anomaly can be explained by pseudoscalar DM which induces an oscillating electric dipole moment for the muon. This explanation may be verified with a time-resolved analysis.