Tri-bimaximal Neutrino Mixing and CKM Matrix in a SU(5)x(d)T Model

TL;DR

This paper introduces a predictive SU(5)x(d)T model that explains neutrino mixing, quark mixing, and fermion mass hierarchies, while suppressing proton decay operators, with testable predictions for mixing angles.

Contribution

The model uniquely combines tri-bimaximal leptonic mixing with realistic CKM quark mixing within a constrained symmetry framework, providing a dynamical origin for fermion mass hierarchies.

Findings

Predicts theta13 ~ theta_c/3sqrt{2}

Derives a sum rule for solar mixing angle deviation

Suppresses proton decay operators via Z12 x Z12' symmetry

Abstract

In this talk, we present a model based on SU(5)x(d)T which successfully gives rise to near tri-bimaximal leptonic mixing as well as realistic CKM matrix elements for the quarks. The Georgi-Jarlskog relations for three generations are also obtained. Due to the (d)T transformation property of the matter fields, the b-quark mass can be generated only when the (d)T symmetry is broken, giving a dynamical origin for the hierarchy between m_b and m_t. There are only nine operators allowed in the Yukawa sector up to at least mass dimension seven due to an additional Z12 x Z12' symmetry, which also forbids, up to some high orders, operators that lead to proton decay. The resulting model has a total of nine parameters in the charged fermion and neutrino sectors, and hence is very predictive. In addition to the prediction for theta13 ~ theta_c/3sqrt{2}, the model gives rise to a sum rule, tan^2(theta_{solar}) ~ tan^2(theta_{solar,TBM}) - 1/2*theta_c*cos(beta), which is a consequence of the Georgi-Jarlskog relations in the quark sector. This deviation could account for the difference between the experimental best fit value for the solar mixing angle and the value predicted by the tri-bimaximal mixing matrix.