Constraining $A_4$ Leptonic Flavour Model Parameters at Colliders and Beyond

TL;DR

This paper investigates constraints on an $A_4$ leptonic flavour model by combining experimental limits from charged lepton flavour violation, collider searches, and muon magnetic moment measurements, highlighting complementary exclusion regions.

Contribution

It provides a comprehensive analysis of how collider and low-energy experiments jointly constrain $A_4$ flavour models, including reinterpretation of collider data.

Findings

Most stringent constraints come from $ ext{Br}(oldsymbol{ ext{mu} o e ext{gamma}})$ limits and collider searches.

Collider and MEG data constraints are complementary in certain parameter regions.

The analysis identifies parameter space regions excluded by current experiments.

Abstract

The observed pattern of mixing in the neutrino sector may be explained by the presence of a non-Abelian, discrete flavour symmetry broken into residual subgroups at low energies. Many flavour models require the presence of Standard Model singlet scalars which can promptly decay to charged leptons in a flavour-violating manner. We constrain the model parameters of a generic $A_4$ leptonic flavour model using a synergy of experimental data including limits from charged lepton flavour conversion, an 8 TeV collider analysis and constraints from the anomalous magnetic moment of the muon. The most powerful constraints derive from the MEG collaborations' limit on Br$\left(\mu\to e\gamma\right)$ and the reinterpretation of an 8 TeV ATLAS search for anomalous productions of multi-leptonic final states. We quantify the exclusionary power of each of these experiments and identify regions where the constraints from collider and MEG experimental data are complementary.