The T2K Indication of Relatively Large theta_13 and a Natural Perturbation to the Democratic Neutrino Mixing Pattern

TL;DR

This paper explains the T2K experiment's indication of a large theta_13 neutrino mixing angle by perturbing the democratic mixing pattern, predicting a correlation with theta_23, and exploring related parametrizations.

Contribution

It introduces a natural perturbation to the democratic neutrino mixing pattern to account for the large theta_13, including CP violation considerations and testable predictions.

Findings

A correlation between theta_13 and theta_23 is predicted.

The perturbation can explain the large theta_13 without fine-tuning.

Discussion of Wolfenstein-like parametrization of neutrino mixing.

Abstract

The T2K Collaboration has recently reported a remarkable indication of the \nu_\mu -> \nu_e oscillation which is consistent with a relatively large value of \theta_{13} in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of \theta_{13} by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between \theta_{13} and \theta_{23} is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large \theta_{13} at the electroweak scale.