Neutrino non-standard interactions as a portal to test flavour symmetries

TL;DR

This paper explores how non-Abelian discrete flavour symmetries, specifically A4, can influence neutrino non-standard interactions and how experiments like DUNE can test these theoretical models to deepen our understanding of flavour symmetries.

Contribution

It introduces a novel framework linking non-Abelian discrete flavour symmetries to neutrino NSIs, providing new textures and experimental test strategies.

Findings

DUNE can test A4 flavour symmetry through matter-effect NSIs.

UV completions impose additional constraints on NSI textures.

NSI effects, though small, can reveal insights into flavour symmetries.

Abstract

Imposing non-Abelian discrete flavour symmetries to neutrino non-standard interactions (NSIs) is discussed for the first time. For definiteness, we choose $A_4$ as the flavour symmetry, which is subsequently broken to the residual symmetry $Z_2$ in the neutrino sector. We provide a general discussion on flavour structures of NSIs from higher-dimensional operators ($d\leqslant8$) without inducing unnecessary tree-level 4-charged-fermion interactions. Both $A_4$- and $Z_2$-motivated NSI textures are obtained. UV completions of higher-dimensional operators lead to extra experimental constraints on NSI textures. We study the implementation of matter-effect NSIs in DUNE from phenomenological point of view, and discover that DUNE can test $A_4$ with a high level of statistics. We also present exclusion limits of sum rules suggested by UV-complete models. Our result shows that the NSI effects, though predicted to be small for DUNE, could provide useful information that might extend our understanding of the flavour symmetry.