Neutrino magnetic moments, flavor mixing, and the SuperKamiokande solar data

TL;DR

This paper investigates how neutrino magnetic moments influence solar neutrino data, revealing that magnetic scattering effects are unaffected by oscillations in certain cases and establishing a new limit on neutrino magnetic moments using SuperKamiokande data.

Contribution

It provides a new limit on neutrino magnetic moments based on SuperKamiokande data and analyzes the effects of flavor mixing and oscillations on magnetic scattering signals.

Findings

Magnetic neutrino-electron scattering unaffected by oscillations in specific cases.

Effective moments can depend on neutrino energy under MSW mixing.

New limit on neutrino magnetic moment: |5_ u|  1.5  10^{-10} 5 at 90% CL.

Abstract

We find that magnetic neutrino-electron scattering is unaffected by oscillations for vacuum mixing of Dirac neutrinos with only diagonal moments and for Majorana neutrinos with two flavors. For MSW mixing, these cases again obtain, though the effective moments can depend on the neutrino energy. Thus, e.g., the magnetic moments measured with $\bar{\nu}_e$ from a reactor and $\nu_e$ from the Sun could be different. With minimal assumptions, we find a new limit on $\mu_{\nu}$ using the 825-days SuperKamiokande solar neutrino data: $|\mu_{\nu}| \le 1.5\times 10^{-10} \mu_B$ at 90% CL, comparable to the existing reactor limit.