Probing the non-standard neutrino interactions using quantum statistics

TL;DR

This paper investigates how quantum statistical properties and non-standard interactions of neutrinos can be used to distinguish between Dirac and Majorana neutrinos, providing a model-independent framework and potential experimental signatures.

Contribution

It introduces the Dirac Majorana confusion theorem and explores deviations caused by non-standard neutrino interactions, offering new methods to detect or constrain such couplings.

Findings

Non-standard interactions can be constrained using 3-body decays.

The Dirac Majorana confusion theorem explains experimental challenges.

Deviations from the theorem can reveal the nature of neutrinos.

Abstract

Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the ``Dirac Majorana confusion theorem (DMCT)'' showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of non-standard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, $Z \to \nu \, \overline{\nu}$ and $\mathcal{P}_i \to \mathcal{P}_f \, \nu \, \overline{\nu}$ (with $\mathcal{P}_{i,f}$ denoting pseudoscalar mesons, such as $B,K,\pi$). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities.