Neutrino nonstandard interactions as a portal to test flavor symmetries.

Imposing non-Abelian discrete flavor symmetries on neutrino nonstandard interactions (NSIs) is discussed for the first time. For definiteness, we choose A4 as the flavor symmetry, which is subsequently broken to the residual symmetry Z2 in the neutrino sector. We provide a general discussion on the flavor structures of NSIs from higher-dimensional operators (d ≤ 8) without inducing unnecessary tree-level fourcharged-fermion interactions. Both A4- and Z2-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 a phenomenological point of view, and discover that DUNE can test A4 with a high level of statistics. We also present the exclusion limits of sum rules suggested by UV-complete models. Our results show that the NSI effects, though predicted to be small for DUNE, could provide useful information that might extend our understanding of the flavor symmetry.