Light top quark and light charged higgs revisited

Abstract

A model with two Higgs doublets is presented where a discrete symmetry is imposed so that the flavor-changing neutral currents in the down-quark sector are naturally suppressed and obey a hierarchy determined by the hierarchy of the Kobayashi-Maskawa matrix elements. The fermion couplings to charged-Higgs bosons are different from those in models with natural flavor conservation. As a consequence, it is possible to have a light top quark which evades the Tevatron limit by decaying predominantly into a light charged Higgs with mass M_H ≤ m_t - m_b. The model is also consistent with data on ε and B⁰-B̅⁰ mixing for a wide range of M_H and the ratio of vacuum expectation values of the scalar fields.