Constraints on two-Higgs-doublet models at large tanβ from W and Z decays

We study constraints on type-II two-Higgs-doublet models at large tanβ from CERN LEP and SLD Z-pole data and from lepton universality violation in W decay. We perform a global fit and find that, in the context of Z decay, the LEP–SLD experimental values for lepton universality violation, R_b, and A_b all somewhat disfavor the model. Contributions from the neutral-Higgs sector can be used to constrain the scalar–pseudoscalar Higgs mass splittings. Contributions from the charged-Higgs sector allow us to constrain the charged-Higgs boson mass. For tanβ=100 we obtain the 1σ classical (Bayesian) bounds of m_H^±>~670GeV (370GeV) and 1>~m_h⁰/m_A⁰|_α=β=m_H⁰/m_A⁰|_α=0>~0.68 (0.64). The 2σ bounds are weak. Currently, the Fermilab Tevatron experimental limits on lepton universality violation in W decay provide no significant constraint on the Higgs sector.