The Simplest and Most Predictive Model of Muon $g-2$ and Thermal Dark Matter

Understand

The long-standing $4.2 \, \sigma$ muon $g-2$ anomaly may be the result of a new particle species which could also couple to dark matter and mediate its annihilations in the early universe.

• In models where both muons and dark matter carry equal charges under a $U(1)_{L_\mu-L_\tau}$ gauge symmetry, the corresponding $Z^\prime$ can both resolve the observed $g-2$ anomaly and yield an acceptable dark matter relic abundance, relying on annihilations which take place through the $Z^\prime$ resonance.
• Once the value of $(g-2)_{\mu}$ and the dark matter abundance are each fixed, there is very little remaining freedom in this model, making it highly predictive.
• We provide a comprehensive analysis of this scenario, identifying a viable range of dark matter masses between approximately 10 and 100 MeV, which falls entirely within the projected sensitivity of several accelerator-based experiments, including NA62, NA64$\mu$, $M^3$, and DUNE.