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 $tan\beta$. We consider low-energy data relating to $B_d^0-{\overline{B}}_d^0$, $D^0-{\overline{D}}^0$, and $K^0-{\overline{K}}^0$ mixing, and high-energy measurements at $p\overline{p}$ 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 $m_t>77\mathrm{}$ GeV can probably not be evaded by appealing to $t\to b{H}^{+}$ decays, since only a very small sliver of parameter space is consistent with $m_t<77\mathrm{}$ GeV in this scenario. Consistency with either the CERN NA31 or Fermilab E731 $\frac{{\epsilon }^{\prime }}{\epsilon }$ measurements is possible. The rare decays $B\to K^{*}\gamma$, $K^{+}\to {\pi }^{+}\nu \overline{\nu }$, and $K_L\to \mu \mu$ are also examined in these models within the context of our combined analysis.