Low-energy effects of charged Higgs bosons with general Yukawa couplings

We study a model with two Higgs doublets where FCNC`s are allowed at the tree level. In this model, the interactions of charged Higgs bosons with fermions ({ital H}{sup {plus_minus}}{ital f{bar f}}{prime}) include a term that is not proportional to the fermion masses, which we constrain using the following low-energy processes: (i) {tau} decays ({tau}{r_arrow}{nu}{sub {tau}}{ital e}{nu}{sub {ital e}},{nu}{sub {tau}}{mu}{nu}{sub {mu}},{nu}{sub {tau}}{pi}), (ii) leptonic decays of pseudoscalar mesons ({pi},{ital K}{r_arrow}{ital l}{nu}{sub {ital l}}), and (iii) semileptonic {ital b} decays. With these constraints it is possible to make predictions; we illustrate this by presenting the rates for the (FCNC) decay {ital c}{r_arrow}{ital u}+{gamma}, the (second class-current) decay {tau}{r_arrow}{nu}{sub {tau}}+{eta}{pi}, and also the theoretical value of the neutron lifetime.