Restrictions on two-Higgs-doublet models from heavy-quark systems

We obtain bounds on charged-Higgs-boson masses and couplings in models with two Higgs doublets by considering their effect on neutral-B-meson mixing. Even with the present fairly loose experimental constraints, the bounds are comparable to those obtained with additional assumptions from the neutral-K system. Neutral-Higgs-boson effects on the spectrum and wave functions of t t-bar bound states are examined in the same model. In the future they could lead to restrictions on, or discovery of, the corresponding neutral Higgs bosons if they have relatively low masses and enhanced couplings