Supersymmetric type-III seesaw: lepton flavour violating decays and dark matter

TL;DR

This paper explores a supersymmetric type-III seesaw model, analyzing its impact on neutrino masses, lepton flavor violation, dark matter, and how it alters the supersymmetric spectrum compared to standard models.

Contribution

It introduces a supersymmetric type-III seesaw model with three 24 superfields, studying its effects on gauge unification, mass spectra, and experimental constraints.

Findings

The supersymmetric spectrum can significantly differ from mSUGRA predictions.

Lepton flavor violating decay bounds constrain the model's parameter space.

Dark matter relic density constraints further restrict viable regions.

Abstract

We study a supersymmetric version of the seesaw mechanism type-III. The model consists of the MSSM particle content plus three copies of 24 superfields. The fermionic part of the SU(2) triplet contained in the 24 is responsible for the type-III seesaw, which is used to explain the observed neutrino masses and mixings. Complete copies of 24 are introduced to maintain gauge coupling unification. These additional states change the beta functions of the gauge couplings above the seesaw scale. Using mSUGRA boundary conditions we calculate the resulting supersymmetric mass spectra at the electro-weak scale using full 2-loop renormalization group equations. We show that the resulting spectrum can be quite different compared to the usual mSUGRA spectrum. We discuss how this might be used to obtain information on the seesaw scale from mass measurements. Constraints on the model space due to limits on lepton flavour violating decays are discussed. The main constraints come from the bounds on the decay mu to e and gamma but there are also regions where the decay tau to mu and gamma gives stronger constraints. We also calculate the regions allowed by the dark matter constraint. For the sake of completeness, we compare our results with those for the supersymmetric seesaw type-II and, to some extent, with type-I.