Solar $$ {\overline{\nu}}_e $$ flux: revisiting bounds on neutrino magnetic moments and solar magnetic field

Abstract

The interaction of neutrino transition magnetic dipole moments with magnetic fields can give rise to the phenomenon of neutrino spin-flavour precession (SFP). For Majorana neutrinos, the combined action of SFP of solar neutrinos and flavour oscillations would manifest itself as a small, yet potentially detectable, flux of electron antineutrinos coming from the Sun. Non-observation of such a flux constrains the product of the neutrino magnetic moment μ and the strength of the solar magnetic field B. We derive a simple analytical expression for the expected $$ {\overline{\nu}}_e $$ ν ¯ e appearance probability in the three-flavour framework and we use it to revisit the existing experimental bounds on μB. A full numerical calculation has also been performed to check the validity of the analytical result. We also present our numerical results in energy-binned form, convenient for analyses of the data of the current and future experiments searching for the solar $$ {\overline{\nu}}_e $$ ν ¯ e flux. In addition, we give a comprehensive compilation of other existing limits on neutrino magnetic moments and of the expressions for the probed effective magnetic moments in terms of the fundamental neutrino magnetic moments and leptonic mixing parameters.

Summary of Session IV: Neutrino masses, states and interactions

“…Under the assumption of Majorana neutrinos, E. Akhmedov in [10] discussed the conversion of solar electron neutrinos into electron antineutrinos through the combined action of SFP and the ordinary flavour oscillations. By deriving simple analytical expressions [11] he presented revisited experimental bounds on the product of neutrino magnetic moments and the solar magnetic field strength. He also summarised other constraints on neutrino magnetic moments coming from astrophysics, cosmology and laboratory experiments.…”

Shedding light on neutrino self-interactions with solar antineutrino searches

“…Theoretically, solar antineutrinos can be produced through neutrino-antineutrino oscillations [9,10], which were considered as one of the potential solutions to the historical "solar neutrino missing problem" [11,12]. This effect could be significant in the presence of large neutrino magnetic moments and the solar magnetic field [13][14][15][16][17][18]. In addition, solar antineutrinos might also be produced via neutrino decay or DM annihilation in the Sun -see e.g.…”