Exploring leptophilic dark matter with NA64-μ

We investigate the prospects for detecting light leptophilic dark sectors with a missing-momentum experiment at NA64 running in muon mode. In particular, we consider models in which dark matter connects to the visible sector through a lepton- or muon-specific scalar mediator. These scalars can also account for the ∼ 3.5σ discrepancy between the measured and predicted values of (g −2)μ. We emphasize the complementarity between NA64-μ and other terrestrial and astrophysical probes.