http://arxiv.org/abs/2107.09067
The longstanding $4.2 \, \sigma$ 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. Furthermore, portions of this mass range predict contributions to $\Delta N{\rm eff}$ which could ameliorate the tension between early and late time measurements of the Hubble constant, and which could be tested by Stage 4 CMB experiments.
I. Holst, D. Hooper and G. Krnjaic
Wed, 21 Jul 21
30/83
Comments: 5 pages, 4 figures, 2 supplements
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