Distinguishing Dirac and Majorana neutrinos with astrophysical fluxes

TL;DR

This paper explores how astrophysical magnetic fields can alter neutrino helicities, enabling the distinction between Dirac and Majorana neutrinos through observable effects on neutrino fluxes and spectra.

Contribution

It demonstrates that neutrino helicity changes due to magnetic interactions can be used to differentiate Dirac and Majorana neutrinos using astrophysical observations.

Findings

Helicity changes affect neutrino detection signals.

Differences in spectra can distinguish neutrino types.

Even tiny magnetic moments cause measurable effects.

Abstract

Massive neutrinos can have helicity $s_{\parallel}\neq -1$. Neutrino helicity changes when the neutrino interacts with an external magnetic field and it is possible that the left-handed neutrinos born inside the Sun or a supernova could leave their sources with a different helicity. Since Dirac and Majorana neutrinos have different cross sections in the scattering on electrons for different neutrino helicities, a change in the final neutrino helicity may generate a different number of events and spectra in terrestrial detectors when astrophysical neutrinos have travelled regions with strong magnetic fields. In this work, we show that looking for these effects in solar neutrinos, it could be possible to set bounds in the neutrino properties such as the neutrino magnetic moment. Furthermore, for neutrinos coming from a supernova, we show that even in the case of an extremely small neutrino magnetic moment, $\mu_\nu \sim 10^{-19}\mu_B$, there will be measurable differences in both the number of events and in the spectra of Majorana and Dirac neutrinos.