Discrete Flavour Groups, \theta_13 and Lepton Flavour Violation

TL;DR

This paper reviews how discrete flavour groups predict neutrino mixing angles, especially 3, compares these predictions with experimental data, and explores implications for lepton flavour violation within a supersymmetric framework.

Contribution

It provides a comparative analysis of discrete flavour models' predictions for 3 and examines their impact on lepton flavour violating processes in supersymmetry.

Findings

Models with discrete flavour groups can predict 3 within experimental bounds.

Lepton flavour violation constraints favor heavy SUSY scales and small tan().

Reproducing muon g-2 remains challenging under these constraints.

Abstract

Discrete flavour groups have been studied in connection with special patterns of neutrino mixing suggested by the data, such as Tri-Bimaximal mixing (groups A4, S4...) or Bi-Maximal mixing (group S4...) etc. We review the predictions for sin(\theta_13) in a number of these models and confront them with the experimental measurements. We compare the performances of the different classes of models in this respect. We then consider, in a supersymmetric framework, the important implications of these flavour symmetries on lepton flavour violating processes, like \mu -> e gamma and similar processes. We discuss how the existing limits constrain these models, once their parameters are adjusted so as to optimize the agreement with the measured values of the mixing angles. In the simplified CMSSM context, adopted here just for indicative purposes, the small tan(beta) range and heavy SUSY mass scales are favoured by lepton flavour violating processes, which makes it even more difficult to reproduce the reported muon g-2 discrepancy.