Perturbing exactly tri-bimaximal neutrino mixings with charged lepton mass matrices

TL;DR

This paper investigates how charged lepton mass matrices can perturb the ideal tri-bimaximal neutrino mixing pattern, predicting small deviations consistent with current experimental constraints and highlighting the role of charged lepton textures.

Contribution

It introduces a framework where charged lepton mass textures cause deviations from tri-bimaximal neutrino mixing without affecting certain mixing angles, providing new insights into lepton flavor structure.

Findings

Deviations in atmospheric mixing can occur independently of theta_13 and theta_12.

A small sin^2(2 theta_13) <= 0.01 is favored by precise theta_12 measurements.

Charged lepton textures control the magnitude of deviations from tri-bimaximal mixing.

Abstract

We study perturbations of exactly tri-bimaximal neutrino mixings under the assumption that they are coming solely from the charged lepton mass matrix. This may be plausible in scenarios where the mass generation mechanisms of neutrinos and charged leptons/quarks have a different origin. As a working hypothesis, we assume mass textures which may be generated by the Froggatt-Nielsen mechanism for the charged lepton and quark sectors, which generically leads to strong hierarchies, whereas the neutrino sector is exactly tri-bimaximal with a mild (normal) hierarchy. We find that in this approach, deviations from maximal atmospheric mixing can be introduced without affecting theta_13 and theta_12, whereas a deviation of theta_13 or theta_12 from its tri-bimaximal value will inevitably lead to a similar-sized deviation of the other parameter. Therefore, the already very precise knowledge of theta_12 points towards small sin^2(2 theta_13) <= 0.01. The magnitude of this deviation can be controlled by the specific form of the charged lepton texture.