Lepton-specific two-Higgs-doublet model: Experimental constraints and implication on Higgs phenomenology

Abstract

We examine various direct and indirect constraints on the lepton-specific two-Higgs-doublet model and scrutinize the property of the Higgs bosons in the allowed parameter space. We find that in the allowed parameter space the $CP$-odd Higgs boson $A$ is rather light (${m}_{A}<30\text{ }\text{ }\mathrm{GeV}$ with 95% possibility), which is composed dominantly by the leptonic Higgs and decays dominantly into ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$; while the standard-model-like Higgs boson $h$ (responsible largely for electroweak symmetry breaking) decays dominantly in the mode $h\ensuremath{\rightarrow}AA\ensuremath{\rightarrow}4\ensuremath{\tau}$ with a large decay width, which will make the Higgs discovery more difficult at the LHC, whereas this scenario predicts a branching ratio $\mathrm{Br}(Z\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}A)$ ranging from ${10}^{\ensuremath{-}5}$ to ${10}^{\ensuremath{-}4}$, which may be accessible at the GigaZ option of the International Linear Collider.