An $S_3$ Model for Lepton Mass Matrices with Nearly Minimal Texture

TL;DR

This paper introduces an $S_3$ symmetry-based extension of the Standard Model that achieves a nearly minimal lepton mass matrix texture, successfully explaining lepton masses and mixing without fine-tuning.

Contribution

It presents a novel $S_3$ symmetry model with additional $Z_5$ and $Z_3$ symmetries, realizing a nearly minimal Fritzsch-type texture for lepton mass matrices.

Findings

Accommodates observed lepton masses and mixing angles.

Allows for quasidegenerate or inverted neutrino mass spectrum.

Retains successful features of minimal textures without fine-tuning.

Abstract

We propose a simple extension of the electroweak standard model based on the discrete $S_3$ symmetry that is capable of realizing a nearly minimal Fritzsch-type texture for the Dirac mass matrices of both charged leptons and neutrinos. This is achieved with the aid of additional $Z_5$ and $Z_3$ symmetries, one of which can be embedded in $U(1)_{B-L}$. Five complex scalar singlet fields are introduced in addition to the SM with right-handed neutrinos. Although more general, the modified texture of the model retains the successful features of the minimal texture without fine-tuning; namely, it accommodates the masses and mixing of the leptonic sector and relates the emergence of large leptonic mixing angles with the seesaw mechanism. For large deviations of the minimal texture, both quasidegenerate spectrum or inverted hierarchy are allowed for neutrino masses.