Lepton Flavor Violation in Predictive Supersymmetric GUT Models

Abstract

There have been many theoretical models constructed which aim to explain the neutrino masses and mixing patterns. While many of the models will be eliminated once more accurate determinations of the mixing parameters, especially $\sin^2 2\theta_{13}$, are obtained, charged lepton flavor violation (LFV) experiments are able to differentiate even further among the models. In this paper, we investigate various rare LFV processes, such as $\ell_{i} \to \ell_{j} + \gamma$ and $\mu-e$ conversion, in five predictive supersymmetric (SUSY) SO(10) models and their allowed soft-SUSY breaking parameter space in the constrained minimal SUSY standard model. Utilizing the Wilkinson Microwave Anisotropy Probe dark matter constraints, we obtain lower bounds on the branching ratios of these rare processes and find that at least three of the five models we consider give rise to predictions for $\mu \to e + \gamma$ that will be tested by the MEG Collaboration at PSI. In addition, the next generation $\mu-e$ conversion experiment has sensitivity to the predictions of all five models, making it an even more robust way to test these models. While generic studies have emphasized the dependence of the branching ratios of these rare processes on the reactor neutrino angle $\theta_{13}$ and the mass of the heaviest right-handed neutrino $M_3$, we find very massive $M_3$ is more significant than large $\theta_{13}$ in leading to branching ratios near to the present upper limits.