Friedberg-Lee symmetry and tri-bimaximal neutrino mixing in the inverse seesaw mechanism

TL;DR

This paper explores how Friedberg-Lee symmetry combined with the inverse seesaw mechanism can naturally produce the tri-bimaximal neutrino mixing pattern at the TeV scale, with potential for CP violation.

Contribution

It introduces a novel approach linking Friedberg-Lee symmetry with the inverse seesaw to explain neutrino mixing and mass patterns, including the possibility of a massless neutrino.

Findings

Friedberg-Lee symmetry implies one neutrino is massless.

Tri-bimaximal mixing can be achieved with broken FL and exact bc- symmetry.

Non-unitary corrections and CP violation are possible at the TeV scale.

Abstract

The inverse seesaw mechanism with three pairs of gauge-singlet neutrinos offers a natural interpretation of the tiny masses of three active neutrinos at the TeV scale. We combine this picture with the newly-proposed Friedberg-Lee (FL) symmetry in order to understand the observed pattern of neutrino mixing. We show that the FL symmetry requires only two pairs of the gauge-singlet neutrinos to be massive, implying that one active neutrino must be massless. We propose a phenomenological ansatz with broken FL symmetry and exact \mu-\tau symmetry in the gauge-singlet neutrino sector and obtain the tri-bimaximal neutrino mixing pattern by means of the inverse seesaw relation. We demonstrate that non-unitary corrections to this result are possible to reach the percent level and a soft breaking of \mu-\tau symmetry can give rise to CP violation in such a TeV-scale seesaw scenario.