Explaining gμ−2 and RK(*) using the light mediators of U(1)T3R

Scenarios in which right-handed light Standard Model fermions couple to a new gauge group, $U(1{)}_{T3R}$, can naturally generate a sub-GeV dark matter candidate. But such models necessarily have large couplings to the Standard Model, generally yielding tight experimental constraints. We show that the contributions to ${g}_{\ensuremath{\mu}}\ensuremath{-}2$ from the dark photon and dark Higgs largely cancel out in the narrow window where all the experimental constraints are satisfied, leaving a net correction that is consistent with recent measurements from Fermilab. These models inherently violate lepton universality, and UV completions of these models can include quark flavor violation that can explain ${R}_{{K}^{(*)}}$ anomalies as observed at the LHCb experiment after satisfying constraints on $\mathrm{Br}({B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ and various other constraints in the allowed parameter space of the model. This scenario can be probed by FASER, SeaQuest, SHiP, LHCb, Belle, etc.