Muon specific two-Higgs-doublet model

We investigate a new type of a two-Higgs-doublet model as a solution of the muon g - 2 anomaly. We impose a softly-broken Z(4) symmetry to forbid tree level flavor changing neutral currents in a natural way. This Z(4) symmetry restricts the structure of Yukawa couplings. As a result, extra Higgs boson couplings to muons are enhanced by a factor of tan beta, while their couplings to all the other standard model fermions are suppressed by cot beta. Thanks to this coupling property, we can avoid the constraint from leptonic tau decays in contrast to the lepton specific two-Higgs-doublet model, which can explain the muon g - 2 within the 2 sigma level but cannot within the 1s level due to this constraint. We find that the model can explain the muon g - 2 within the 1 sigma level satisfying constraints from perturbative unitarity, vacuum stability, electroweak precision measurements, and current LHC data.