Modular Invariant Models of Lepton Masses at Levels 4 and 5

TL;DR

This paper develops modular invariant models for lepton masses at levels 4 and 5, incorporating flavons and minimal parameters to match experimental data and predict neutrino properties.

Contribution

It introduces novel modular invariant lepton mass models at levels 4 and 5, utilizing flavons and minimal parameters for improved phenomenological accuracy.

Findings

Successfully reproduces lepton mass hierarchy at level 4

Achieves compatibility with experimental neutrino data

Predicts neutrino masses and CP phases

Abstract

We explore alternative descriptions of the charged lepton sector in modular invariant models of lepton masses and mixing angles. In addition to the modulus, the symmetry breaking sector of our models includes ordinary flavons. Neutrino mass terms depend only on the modulus and are tailored to minimize the number of free parameters. The charged lepton Yukawa couplings rely upon the flavons alone. We build modular invariant models at levels 4 and 5, where neutrino masses are described both in terms of the Weinberg operator or through a type I seesaw mechanism. At level 4, our models reproduce the hierarchy among electron, muon and tau masses by letting the weights play the role of Froggatt-Nielsen charges. At level 5, our setup allows the treatment of left and right handed charged leptons on the same footing. We have optimized the free parameters of our models in order to match the experimental data, obtaining a good degree of compatibility and predictions for the absolute neutrino masses and the $CP$ violating phases. At a more fundamental level, the whole lepton sector could be correctly described by the simultaneous presence of several moduli. Our examples are meant to make a first step in this direction.