A hybrid seesaw model and hierarchical neutrino flavor structures based on $A_{4}$ symmetry

TL;DR

This paper introduces a hybrid seesaw model with $A_{4}$ symmetry that explains neutrino mass hierarchies, predicts observable neutrinoless double beta decay signals, and proposes a dark matter candidate arising from symmetry breaking.

Contribution

It presents a novel hybrid seesaw framework based on $A_{4}$ symmetry, combining tree-level and one-loop mechanisms to produce hierarchical neutrino masses and a dark matter candidate.

Findings

Hierarchical neutrino mass structures can produce large effective neutrino masses.

The model predicts observable signals in next-generation neutrinoless double beta decay experiments.

A dark matter candidate emerges from symmetry breaking, with its relic abundance and detection cross section analyzed.

Abstract

We propose a hybrid seesaw model based on $A_{4}$ flavor symmetry, which generates a large hierarchical flavor structure. In our model, tree-level and one-loop seesaw mechanisms predict different flavor structures in the neutrino mass matrix, and generate a notable hierarchy among them. We find that such a hierarchical structure gives a large effective neutrino mass which can be accessible by next-generation neutrinoless double beta decay experiments. Majorana phases can also be predictable. The $A_{4}$ flavor symmetry in the model is spontaneously broken to the $Z_{2}$ symmetry, leading to a dark matter candidate which is assumed to be a neutral scalar field. The favored mass region of the dark matter is obtained by numerical computations of the relic abundance and the cross section of the nucleon. We also investigate the predictions of the several hierarchical flavor structures based on $A_{4}$ symmetry for the effective neutrino mass and the Majorana phases, and find the characteristic features depending on the hierarchical structures.