Prospects of Z′ portal dark matter in U(1)Lμ−Lτ

Abstract

The gauged U(1)Lμ−Lτ model is well motivated to explain the muon g−2 anomaly and dark matter in previous studies. However, the latest NA64μ experiment has almost excluded all the parameter space for the muon g−2, which indicates that the light dark matter benchmark scenarios interpreting muon g−2 in previous studies are under significant pressure at present. In light of many recent and future experimental results, we revisit the minimal Z′ portal dark matter in U(1)Lμ−Lτ. Focusing on the phenomenology of dark matter χ, we first explore the viable parameter space for light dark matter under various tight constraints. Around the Z′ resonance, we find that there is still a large parameter space for mχ≳10  MeV via thermal freeze-out. On the other hand, the constraints on Z′ above the electroweak scale are quite loose, but are less studied for dark matter. We also investigate the heavy dark matter around the TeV scale and corresponding constraints. A large part of the parameter space for dark matter is within the reach of future experiments. Published by the American Physical Society 2025