Naturally suppressed flavor violations in models with two Higgs doublets

Abstract

A class of SU(2)×U(1) models with two Higgs doublets and appropriate discrete symmetry are considered. Unlike the conventional discrete symmetry, which eliminates flavor changing neutral currents (FCNC), the imposed symmetry naturally leads to suppression and the hierarchy |F₁₂|<|F₁₃|<|F₂₃| in the flavor changing couplings F_ij of Higgs to generations i and j. As a consequence, the lower bound of O(TeV) on Higgs masses coming from processes like K_L→μ⁺μ⁻ and K⁰−K̅⁰ mixing gets relaxed and hence pertubative unitarity is not violated in these models, unlike in conventional models with FCNSs. Restrictions on KM elements following from ε B⁰−B̅⁰ and mixing are studied in cases where neutral Higgs provide a significant contribution to the latter.