NEW CONSTRAINTS ON THE CHARGED HIGGS SECTOR IN 2-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. We consider low-energy data relating to Bd0-B»d0, 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 ET. 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 mt>77 GeV can probably not be evaded by appealing to tbH+ decays, since only a very small sliver of parameter space is consistent with mt<77 GeV in this scenario. Consistency with either the CERN NA31 or Fermilab E731 μμ measurements is possible. The rare decays BK*, K+, and KL are also examined in these models within the context of our combined analysis. © 1990 The American Physical Society.