Anomalous Higgs Yukawa Couplings from Radiative Masses and Related Phenomena
The experimentally accessible branching fractions of the 125 GeV particle discovered in 2012 are consistent with the Higgs boson of the standard model (SM), but they are not yet conclusive due to large experimental uncertainties. Of particular interest are the inferred Yukawa couplings of the Higgs boson to a heavy quark or charged lepton. In the SM, this is given by a tree-level expression in which the Yukawa coupling is proportional to the fermion mass. We consider instead a radiative origin of fermion mass which occurs in one loop through dark matter. It is shown that the effective Higgs Yukawa coupling can have significant deviations from the SM, with potential consequences for Higgs production and decay. The radiative model also explains the muon anomalous magnetic moment, with predictions for rare lepton decays in parallel with a radiative model of neutrino mass based on the inverse seesaw. Also considered are three other possible extensions of the SM, with tree-level masses for charged fermions: A Higgs triplet model of radiative neutrino mass with dark matter and collider phenomenology, a vector dark matter model with relic density and direct detection analysis, and a supersymmetric model which relaxes the constraints on the Higgs mass and accommodates the recent 750 GeV diphoton excess.