An A_5 Model of Four Lepton Generations

TL;DR

This paper develops an $A_5$ flavor symmetry model for four lepton generations, extending previous $A_4$ models, predicting neutrino mass relations, and explaining the electron mass via quantum corrections.

Contribution

It introduces a novel $A_5$ based four-generation lepton model that retains key features of $A_4$ models and predicts specific neutrino mass relations.

Findings

Predicts $m_{\nu_1} = m_{\nu_3}$ and $m_{\nu_2} = 0$ at leading order.

Neutrino mass splitting arises from breaking $A_5$ to $A_4$.

Electron mass generated through quantum corrections.

Abstract

We study the lepton sector of a four generations model based on the discrete flavor group $A_5$ (the even permutation of five objects). The best features of the three family $A_4$ model survive, including the tribimaximal pattern of three generation neutrino mixings. At leading order the three light neutrino mass relations of $m_{\nu_1} = m_{\nu_3}$ and $m_{\nu_2} = 0$ are predicted. The splitting of the neutrino masses can be naturally obtained as a result of the breaking of $A_{5}$ down to $A_4$ and a degenerate spectrum is preferred in our model. In our $A_5$ model, the electron mass is zero at tree level, but calculable through quantum corrections.