Distinguishing Dirac and Majorana neutrinos with astrophysical fluxes

Abstract

Massive neutrinos can have helicity . 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 of 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 traveled through regions with strong magnetic fields. In this work, we show that in 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, μν ∼ 10−19μB, there could be measurable differences in both the number of events and in the spectra of Majorana and Dirac neutrinos as soon as accurate supernova models reduce uncertainties in the neutrino flux predictions.