Restricting Majorana phases in the Tri-Bi-Maximal limit

TL;DR

This paper investigates how deviations from the Tri-Bi-Maximal neutrino mixing pattern can accommodate current experimental data, constraining Majorana phases and predicting neutrinoless double beta decay amplitudes.

Contribution

It introduces specific correction matrices to the Tri-Bi-Maximal pattern, linking Dirac and Majorana CP phases and providing testable predictions for neutrinoless double beta decay.

Findings

Constraints on Majorana phases from corrected mixing patterns

Predicted sharp regions for neutrinoless double beta decay amplitude

Compatibility with latest neutrino mixing data

Abstract

The Tri-Bi-Maximal pattern has been long investigated as the symmetric scenario that lies behind the neutrino mixing matrix. It predicts a null reactor angle and hence forbids $CP$ violation in the lepton sector, which is in contrast to the current experimental determinations. We explore different deviations from this pattern to restore the compatibility with the latest fits of neutrino mixing parameters. We consider two unitary matrices to correct the symmetric pattern, each of them is written in terms of one single angle and one complex phase, which will be constrained by the experimental mixings and from symmetry restrictions in the mass matrix. We note that these correction parameters would allow us to obtain simultaneous information about the Dirac and Majorana $CP$ phases in some specific scenarios. We show that the predicted values lead to sharped regions for the neutrinoless double beta decay amplitude, in the selected cases, that could be tested with forthcoming results.