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

We study lepton-number-violating (LNV) decays of heavy flavors (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 tau(-) -> l(+)M(1)(-)M(2)(-) 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 -> bl(+)l(+)W(-) turn out to be at the level of similar to 10(-7) - 10(-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. DOI: 10.1103/PhysRevD.87.056005