Non-unitary leptonic mixing and CP-violation

TL;DR

This paper explores how non-unitary leptonic mixing matrices, arising from new physics theories for neutrino masses, can be effectively probed through CP asymmetries in the muon to tau neutrino oscillation channel, linking to non-standard interactions.

Contribution

It demonstrates that CP asymmetries in $ u_ o u_ au$ are powerful probes of non-unitary mixing and clarifies their relation to non-standard neutrino interactions.

Findings

CP asymmetries in $ u_ o u_ au$ are sensitive to non-unitary mixing.

The framework applies to non-standard neutrino interactions with minimal fine-tuning.

Provides a method to test new physics in neutrino oscillations.

Abstract

Some theories of new physics accounting for neutrino masses can give rise to a low-energy non-unitary leptonic mixing matrix. It is shown that the CP-asymmetries in the $\nu_\mu\to \nu_\tau$ channel are an excellent probe of such new physics. In adition, we clarify the relationship betweeen our framework and the so called "non-standard neutrino interactions" scenarios: the sensitivities explored here apply as well to such constructions, except for extremely fine-tuned cancellations.