The Electron/Muon Specific Two Higgs Doublet Model at e+ e- Colliders

Recently, Kajiyama, Okada and Yagyu (KOY) proposed an electron/muon specific two Higgs doublet model. In this model, an S3 symmetry suppresses flavor changing neutral currents instead of a Z2 symmetry. In the "Type I" version of the model, the heavy Higgs bosons have a greatly enhanced coupling to electrons and muons. KOY studied the phenomenology of the heavy Higgs bosons at the LHC. In this paper, the phenomenology at electron-positron colliders is studied. For the heavy Higgs mass range between 150 and 210 GeV, bounds from LEP-200 are stronger than those from the LHC. The model allows for the interesting possibility that muon pair production at the ILC can be mediated by s-channel Higgs exchange. This requires an energy scan. The scanning rate and necessary resolution are discussed.