Solar neutrinos at keV energies: thermal flux¹

Abstract

The neutrino flux at Earth is dominated in the keV energy range by the neutrinos produced in the Sun through thermal processes, namely photo production, bremsstrahlung, plasmon decay, and emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. Such a component of the neutrino flux is conspicuously absent from popular analyses of the all-sources spectrum at Earth, whereas if detected it could be a source of information about solar physics. Moreover, it would be the relevant background for keV-mass sterile neutrino dark matter direct searches.1 The results quoted here were obtained in reference [1] and presented by E. Vitagliano at TAUP 2017.

Sensitivity to neutrino-antineutrino transitions for boron neutrinos

“…Besides all above mentioned backgrounds, the thermal neutrino flux [26] from the Sun and the solar atmospheric neutrinos [27] may contribute to electron antineutrinos but mostly in different energy orders, keV and GeV respectively, in comparison with typical IBD energies. The solar thermal neutrino flux comes from the electromagnetic interaction of the particles constituting plasma.…”