Lepton-number-violating decays of heavy flavors induced by doubly-charged Higgs boson

Abstract

We study lepton-number-violating (LNV) decays of heavy flavors ($\ensuremath{\tau}$ lepton and top quark) induced by a doubly-charged Higgs boson in the Higgs triplet model. It is found that the branching fractions of LNV ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{M}_{1}^{\ensuremath{-}}{M}_{2}^{\ensuremath{-}}$ decays are highly suppressed compared with the current experimental limits. On the other hand, for LNV top-quark decays, the most optimistic branching ratios for $t\ensuremath{\rightarrow}b{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{+}{W}^{\ensuremath{-}}$ turn out to be at the level of $\ensuremath{\sim}{10}^{\ensuremath{-}7}\ensuremath{-}{10}^{\ensuremath{-}8}$. The observation of these rare top-quark decays would be a clear signal of LNV processes, and their nonobservation would allow us to constrain the parameters of the Higgs triplet model.