Implications of a light "dark Higgs" solution to the gμ-2 discrepancy

A light scalar ϕ with mass ≲1 GeV and muonic coupling O (1 0^-3) would explain the 3.5 σ discrepancy between the Standard Model (SM) muon g -2 prediction and experiment. Such a scalar can be associated with a light remnant of the Higgs mechanism in the "dark" sector. We suggest ϕ →l⁺l^- bump hunting in μ →e ν ν ¯ϕ , μ^-p →ν_μn ϕ (muon capture), and K^±→μ^±ν ϕ decays as direct probes of this scenario. In a general setup, a potentially observable muon electric dipole moment ≲10^-23 e cm and lepton-flavor-violating decays τ →μ (e )ϕ or μ →e ϕ can also arise. Depending on parameters, a deviation in BR(H →μ⁺μ^-) from SM expectations, due to Higgs coupling misalignment, can result. We illustrate how the requisite interactions can be mediated by weak-scale vector-like leptons that typically lie within the reach of future LHC measurements.