Non-Unitary Neutrino Propagation From Neutrino Decay

TL;DR

This paper explores how neutrino decay into lighter states can lead to non-unitary propagation, affecting flavor change and introducing new CP-violation sources, with implications for neutrino phenomenology.

Contribution

It provides a detailed calculation of transition probabilities in two- and three-flavor scenarios considering non-unitary effects from neutrino decay, highlighting novel phenomenological consequences.

Findings

Neutrino decay can cause non-unitary flavor evolution.

New CP-violation sources arise from decay-induced non-unitarity.

Distinct phenomenological signatures differ from other unitarity violation models.

Abstract

Neutrino propagation in space-time is not constrained to be unitary if very light states - lighter than the active neutrinos - exist into which neutrinos may decay. If this is the case, neutrino flavor-change is governed by a handful of extra mixing and "oscillation" parameters, including new sources of CP-invariance violation. We compute the transition probabilities in the two- and three-flavor scenarios and discuss the different phenomenological consequences of the new physics. These are qualitatively different from other sources of unitarity violation discussed in the literature.