Lepton flavor violating Higgs boson decays from massive seesaw neutrinos

Abstract

Lepton flavor violating Higgs boson decays are studied within the context of seesaw models with Majorana massive neutrinos. Two models are considered: The SM-seesaw, with the Standard Model Particle content plus three right handed neutrinos, and the MSSM-seesaw, with the Minimal Supersymmetric Standard Model particle content plus three right handed neutrinos and their supersymmetric partners. The widths for these decays are derived from a full one-loop diagrammatic computation in both models, and they are analyzed numerically in terms of the seesaw parameters, namely, the Dirac and Majorana mass matrices. Several possible scenarios for these mass matrices that are compatible with neutrino data are considered. In the SM-seesaw case, very small branching ratios are found for all studied scenarios. These ratios are explained as a consequence of the decoupling behaviour of the heavy right handed neutrinos. In contrast, in the MSSM-seesaw case, sizeable branching ratios are found for some of the leptonic flavor violating decays of the MSSM neutral Higgs bosons and for some choices of the seesaw matrices and MSSM parameters. The relevance of the two competing sources of lepton flavor changing interactions in the MSSM-seesaw case is also discussed. The non-decoupling behaviour of the supersymmetric particles contributing in the loop-diagrams is finally shown.Comment: 44pgs. Version to appear in Phys.Rev.

Analysis of the h, H, A → τμ decays induced from SUSY loops within the Mass Insertion Approximation

“…We have further checked that when the large tan β limit is considered in this eq. (3.22), we find agreement with the results found from the full one-loop computation in [37]. Concretely, using eq.…”

“…In this section we analyze the behavior of the radiative corrections from SUSY loops to the LFV neutral Higgs bosons decays h, H, A → τμ, comparing numerically the predictions of the full one-loop calculation [37] with the MIA results, calculated for the first time here. The SUSY mass spectra for the three scenarios considered along this work are computed numerically with the code SPheno [57,58].…”

“…The LFVHD rates are computed with our private FORTRAN code in which we have implemented both the analytic results of the MIA of eqs. (B.1) through (B.8) and also the complete one-loop formulas of [37]. Full -diag.…”

“…On the theoretical side, the subject of LFVHD has been studied for a long time in the literature within various models beyond the SM (for recent works see, for instance, ), but the most frequently explored ones are the supersymmetric (SUSY) models because the needed feature of flavor mixing among particles of different generations to produce these exotic decays is easily incorporated and well justified in the SUSY particles sector [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. More specifically, it is the flavor mixing among the three generations of the charged sleptons and/or sneutrinos, typically present in SUSY models, what produces via their contributions at the one-loop level, these interesting Higgs decay channels with Lepton Flavor Violation (LFV).…”

“…Several examples where the neutrino Yukawa couplings, which can be large if neutrinos are Majorana fermions, are the responsible for generating these LFVHD have been explored in the literature. The issue of LFVHD being radiatively generated from loops with neutrinos was first explored in a non-SUSY context [48], and later other cases were considered, including the case of the type-I seesaw model both with and without SUSY [37], the inverse seesaw model [13] and its SUSY version [47]. The study of LFVHD within the more general context of Non-Minimal-Flavor Violation (NMFV) of the MSSM has also a long story.…”