CKM and Tri-bimaximal MNS Matrices in a SU(5) x (d)T Model

TL;DR

This paper presents a unified SU(5) x (d)T model that naturally explains near tri-bimaximal leptonic mixing, realistic quark mixing, and the fermion mass hierarchy with minimal parameters and high predictivity.

Contribution

It introduces a novel SU(5) x (d)T framework with a Z_{12} x Z'_{12} symmetry, achieving realistic fermion masses, mixings, and a new sum rule for solar mixing angle deviations.

Findings

Predicts heta_{13} oughly heta_{c}/(3 imes ext{sqrt}(2))

Derives a sum rule relating solar mixing angle deviation to the Cabibbo angle

Provides a minimal nine-parameter model with suppressed proton decay operators

Abstract

We propose 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 Z_{12} x Z'_{12} 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 \theta_{13} \simeq \theta_{c}/3 \sqrt{2}, the model gives rise to a sum rule, \tan^{2}\theta_{\odot} \simeq \tan^{2} \theta_{\odot, \mathrm{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.