Discrete Leptonic Flavor Symmetries: UV Mediators and Phenomenology

TL;DR

This paper explores discrete flavor symmetries in the lepton sector, classifies new physics mediators, and analyzes their phenomenological implications, especially for charged lepton flavor violation, within a bottom-up framework.

Contribution

It provides a comprehensive classification of NP mediators and tree-level SMEFT relations for $A_4$, $A_5$, and $S_4$ flavor groups in the leptonic sector.

Findings

Classified NP mediators for discrete flavor groups.

Derived matching relations onto dimension-6 SMEFT operators.

Constrained NP mediators using charged lepton flavor violation data.

Abstract

Given the absence of a definitive top-down indication for understanding the peculiar structure of the lepton sector, discrete flavor symmetries offer a profound perspective for examining the intricate patterns of lepton masses and mixings. In this work, drawing upon previous studies on the interplay of flavor symmetries with the potential UV completions from a purely bottom-up perspective, three well-motivated discrete flavor groups, suitable for portraying the leptonic sector as well as the neutrino masses, specifically $A_4$, $A_5$ and $S_4$, are explored within this framework, leading to the comprehensive classification of the NP mediators, along with the tree-level matching relations onto dimension-6 SMEFT operators. Particular emphasis is placed on the discrete leptonic directions, for which a phenomenological analysis is carried out in order to constrain various NP mediators, where significant focus is directed towards the examination of the cLFV operators, which, for the wide range of applicable cases, offer the leading constraint.