Lepton Flavour Violating Decays tau to lll and mu to e gamma in the Higgs Triplet Model

TL;DR

This paper investigates lepton flavor violating decays mediated by Higgs triplet bosons, analyzing parameter space constraints and potential signals in ongoing experiments, with implications for neutrino mass models and Majorana phases.

Contribution

It provides a detailed analysis of the parameter space allowing LFV signals in the Higgs Triplet Model, considering experimental constraints and neutrino mass parameters.

Findings

LFV decay rates depend on triplet Yukawa couplings and neutrino parameters.

Conditions for observable tau to lll and mu to e gamma decays are identified.

Constraints from mu to eee limit are thoroughly examined, highlighting the role of Majorana phases.

Abstract

Singly and doubly charged Higgs bosons in the Higgs Triplet Model mediate the lepton flavour violating (LFV) decays tau to \bar{l}ll and mu to e gamma. The LFV decay rates are proportional to products of two triplet Yukawa couplings (h_{ij}) which can be expressed in terms of the parameters of the neutrino mass matrix and an unknown triplet vacuum expectation value. We determine the parameter space of the neutrino mass matrix in which a signal for tau to \bar{l}ll and/or mu to e gamma is possible at ongoing and planned experiments. The conditions for respecting the stringent upper limit for mu to eee are studied in detail, with emphasis given to the possibility of |h_{ee}|\simeq 0 which can only be realized if Majorana phases are present.