Muon specific two-Higgs-doublet model

Understand

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 $\cot\beta$.