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

Abstract

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 (${\mathit{H}}^{\ifmmode\pm\else\textpm\fi{}}$ff\ifmmode\bar\else\textasciimacron\fi{}') include a term that is not proportional to the fermion masses, which we constrain using the following low-energy processes: (i) \ensuremath{\tau} decays (\ensuremath{\tau}\ensuremath{\rightarrow}${\ensuremath{\nu}}_{\mathrm{\ensuremath{\tau}}}$e${\ensuremath{\nu}}_{\mathit{e}}$,${\ensuremath{\nu}}_{\mathrm{\ensuremath{\tau}}}$\ensuremath{\mu}${\ensuremath{\nu}}_{\mathrm{\ensuremath{\mu}}}$,${\ensuremath{\nu}}_{\mathrm{\ensuremath{\tau}}}$\ensuremath{\pi}), (ii) leptonic decays of pseudoscalar mesons (\ensuremath{\pi},K\ensuremath{\rightarrow}l${\ensuremath{\nu}}_{\mathit{l}}$), and (iii) semileptonic b decays. With these constraints it is possible to make predictions; we illustrate this by presenting the rates for the (FCNC) decay c\ensuremath{\rightarrow}u+\ensuremath{\gamma}, the (second class-current) decay \ensuremath{\tau}\ensuremath{\rightarrow}${\ensuremath{\nu}}_{\mathrm{\ensuremath{\tau}}}$+\ensuremath{\eta}\ensuremath{\pi}, and also the theoretical value of the neutron lifetime.