Non-unitary Leptonic Flavor Mixing and CP Violation in Neutrino-antineutrino Oscillations

TL;DR

This paper investigates CP violation in neutrino-antineutrino oscillations considering non-unitary flavor mixing, revealing potential deviations from standard predictions due to heavy Majorana neutrino effects.

Contribution

It derives oscillation probabilities and CP asymmetries with non-unitary mixing, highlighting significant deviations from unitary cases based on current experimental bounds.

Findings

CP asymmetries can significantly deviate from unitary predictions

Non-unitary effects are constrained by current experimental bounds

Neutrino-antineutrino oscillations provide a probe for Majorana neutrino properties

Abstract

If massive neutrinos are Majorana particles, then the lepton number should be violated in nature and neutrino-antineutrino oscillations $\nu^{}_\alpha \leftrightarrow \overline{\nu}^{}_\beta$ (for $\alpha, \beta = e, \mu, \tau$) will definitely take place. In the present paper, we study the properties of CP violation in neutrino-antineutrino oscillations with the non-unitary leptonic flavor mixing matrix, which is actually a natural prediction in the canonical seesaw model due to the mixing between light and heavy Majorana neutrinos. The oscillation probabilities $P(\nu^{}_\alpha \to \overline{\nu}^{}_\beta)$ and $P(\overline{\nu}^{}_\alpha \to \nu^{}_\beta)$ are derived, and the CP asymmetries ${\cal A}^{}_{\alpha \beta} \equiv [P(\nu^{}_\alpha \to \overline{\nu}^{}_\beta) - P(\overline{\nu}^{}_\alpha \to \nu^{}_\beta)]/[P(\nu^{}_\alpha \to \overline{\nu}^{}_\beta) + P(\overline{\nu}^{}_\alpha \to \nu^{}_\beta)]$ are also calculated. Taking into account current experimental bounds on the leptonic unitarity violation, we show that the CP asymmetries induced by the non-unitary mixing parameters can significantly deviate from those in the limit of a unitary leptonic flavor mixing.