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 Z4 symmetry to forbid tree level flavor changing neutral currents in a natural way. This Z4 symmetry restricts the structure of Yukawa couplings. As a result, extra Higgs boson couplings to muons are enhanced by a factor of tanβ, while their couplings to all the other standard model fermions are suppressed by cotβ. Thanks to this coupling property, we can avoid the constraint from leptonic τ decays in contrast to the lepton specific two-Higgs-doublet model, which can explain the muon g−2 within the 2σ level but cannot within the 1σ level due to this constraint. We find that the model can explain the muon g−2 within the 1σ level satisfying constraints from perturbative unitarity, vacuum stability, electroweak precision measurements, and current LHC data.
@article{arxiv.1705.01469,
title = {Muon specific two-Higgs-doublet model},
author = {Tomohiro Abe and Ryosuke Sato and Kei Yagyu},
journal= {arXiv preprint arXiv:1705.01469},
year = {2017}
}