A Shift from Democratic to Tri-bimaximal Neutrino Mixing with Relatively Large theta_{13}

TL;DR

This paper explores how small perturbations to the democratic neutrino mixing pattern can naturally produce a nearly tri-bimaximal mixing matrix with a larger theta_{13} angle, aligning with recent experimental hints.

Contribution

It introduces a novel approach to modify the democratic mixing pattern to achieve a larger theta_{13} while maintaining near tri-bimaximal mixing, providing simple viable scenarios.

Findings

Perturbations can produce theta_{13} in the range 5° to 12°.

Two simple scenarios of the mixing matrix are proposed.

Phenomenological implications of these scenarios are discussed.

Abstract

Recent neutrino oscillation data hint that the smallest neutrino mixing angle theta_{13} is possible to lie in the range 5^\circ \lesssim \theta_{13} \lesssim 12^\circ. We show that reasonable perturbations to the democratic mixing pattern, which is geometrically related to the tri-bimaximal mixing pattern through an equal shift \theta_* \simeq 9.7^\circ of two large mixing angles, can naturally produce a nearly tri-bimaximal neutrino mixing matrix V with sufficiently large theta_{13}. Two especially simple but viable scenarios of V are proposed and their phenomenological consequences are discussed.