Paper detail

A $L_μ- L_τ$ theory of Higgs flavor violation and $(g-2)_μ$

Several experiments reported hints for the violation of lepton flavor or lepton flavor universality in processes involving muons. Most prominently, there is the hint for a non-zero rate of the flavor violating Higgs decay $h \to τμ$ at the LHC, as well as the hint for lepton flavor universality violation in rare $B$ meson decays at LHCb. In addition, also the long standing discrepancy in the anomalous magnetic moment of the muon motivates new physics connected to muons. A symmetry which violates lepton flavor universality, is $L_μ-L_τ$: the difference of muon-number and tau-number. We show that adding vector-like fermions to a $L_μ-L_τ$ theory generates naturally an effect in the anomalous magnetic moment of the muon and $h\toτμ$, while effects in other $τ\to μ$ transitions are systematically suppressed by symmetry arguments. We find that if $L_μ-L_τ$ is gauged it is possible to also accommodate the discrepant $b\to sμμ$ data while predicting a $τ\to3μ$ and a modified $h\toμμ$ rate within reach of upcoming experiments.