Approximate magic symmetry in a cobimaximal scenario of Majorana neutrinos

TL;DR

This paper explores an approximate magic symmetry combined with cobimaximal mixing in Majorana neutrinos, constraining CP phases and predicting neutrinoless double beta decay amplitudes.

Contribution

It introduces a novel combined constraint on the neutrino mass matrix from cobimaximal mixing and magic symmetry, highlighting approximate fulfillment and phase restrictions.

Findings

Majorana CP phases are tightly constrained.

Regions in neutrinoless double beta decay amplitude are identified.

Approximate symmetry breaking allows phase determination.

Abstract

The searches for an underlying pattern in neutrino masses have motivated different proposals for textures in the neutrino mass matrix, which is also related to particular arrangements of the mixing matrix. Current experimental determinations of neutrino mixings have restricted some of the most studied proposals. In this work, we propose a new combined constraint on the neutrino mass matrix arising from the cobimaximal mixing and the magic symmetry in a model-independent fashion. We show that both conditions cannot be fulfilled simultaneously in an exact but rather in an approximate way. We have found that the Majorana CP phases are tightly restricted within this approach, leading to well-defined regions in the neutrinoless double beta decay amplitude. The small symmetry breaking requirement allows us to determine the Majorana phases for specific values of the lightest neutrino mass, consistent with current bounds on the mixing angles, neutrinoless double-beta decay, and cosmology results.