Solar $\barν_e$ 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 νe 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 νe 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.

Magnetar-powered neutrinos and magnetic moment signatures at IceCube

“…While such values are essentially experimentally unreachable [6], there are several realizations beyond the Standard Model (BSM) which feature generation of large and testable νMM as well as the small neutrino masses [7][8][9][10][11]. Large νMM can source the excess of neutrino scattering events [10], enhance neutrino decay rates [12,13], impact the physics of the early Universe [14] and influence neutrino propagation in the Sun and supernovae [1,[15][16][17][18][19][20][21]. For latter, magnetic field plays a role in the transition between left-handed and right-handed neutrino states.…”

Neutrino Magnetic Moments Meet Precision $N_{\rm eff}$ Measurements

“…Large NMM have motivated extensive searches in laboratories as well as astrophysical and cosmological observations. Laboratory searches are mostly based on the measurement of low-energy neutrino scattering [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Astrophysical bounds from stellar energy loss, though vulnerable to uncertainties of astrophysical models, have long been stronger than laboratory ones [28].…”