Large neutrino mixing angle \theta_{13}^{MNS} and quark-lepton mass ratios in unified flavour models

TL;DR

This paper explores how charged lepton corrections in unified flavour models can generate a large leptonic mixing angle _{13}^{MNS}, proposing novel Clebsch-Gordan factor combinations that produce predictions aligning with experimental hints.

Contribution

It introduces new combinations of Clebsch-Gordan factors in unified models to generate large _{13}^{MNS} angles, expanding the viable parameter space for neutrino mixing predictions.

Findings

Symmetric mass matrices with zero (1,1)-elements lead to small _{13}^{MNS} (~2.8b0).

Non-symmetric mass matrices with specific Clebsch-Gordan factors can produce _{13}^{MNS} angles up to 10.1b0.

Models with tri-bimaximal or bimaximal neutrino mixing can accommodate these large _{13}^{MNS} predictions.

Abstract

We analyse how a large value of the leptonic mixing angle \theta_{13}^{MNS} can be generated via charged lepton corrections in unified flavour models, using novel combinations of Clebsch-Gordan factors for obtaining viable quark-lepton mass ratios for the first two families. We discuss how these Clebsch-Gordan factors affect the relations between down-type quark mixing and charged lepton mixing in SU(5) GUTs and Pati-Salam unified models and calculate the resulting possible predictions for \theta_{13}^{MNS} for models with \theta_{13}^\nu, \theta_{13}^e << \theta_{12}^e. While symmetric mass matrices with zero (1,1)-elements always lead to comparatively small \theta_{13}^{MNS} \approx 2.8 degrees, we find novel combinations of Clebsch-Gordan factors for non-symmetric mass matrices which can yield \theta_{13}^{MNS} \approx 5.1 degrees, 6.1 degrees, 7.6 degrees or 10.1 degrees, as favoured by the current experimental hints for large \theta_{13}^{MNS}. We discuss applications to classes of models with underlying tri-bimaximal or bimaximal mixing in the neutrino sector.