New constraints on the charged Higgs sector in two-Higgs-doublet models

Two-Higgs-doublet models predict nonstandard physical effects through the interactions of charged Higgs scalars. We analyze the experimental measurements that bound these effects and quantify the resulting constraints on the charged-Higgs-boson mass and coupling parameter tanβ. We consider low-energy data relating to B⁰_d-B¯ ⁰_d, D⁰-D¯ ⁰, and K⁰-K¯ ⁰ mixing, and high-energy measurements at pp¯ colliders relating to searches for the top quark and events with large missing E_T. Our analysis systematically takes account of theoretical uncertainties in bag factors, decay constants, and quark mixing matrix elements by Monte Carlo sampling. We combine our results to determine the regions in the charged-Higgs-boson parameter space that are consistent with present data. An important result is that the Collider Detector at Fermilab top-quark mass bound m_t>77 GeV can probably not be evaded by appealing to t-->bH⁺ decays, since only a very small sliver of parameter space is consistent with m_t<77 GeV in this scenario. Consistency with either the CERN NA31 or Fermilab E731 ɛ'/ɛ measurements is possible. The rare decays B-->K^*γ, K⁺-->π⁺νν¯, and K_L-->μμ are also examined in these models within the context of our combined analysis.