Limiting neutrino magnetic moments with Borexino Phase-II solar neutrino data

TL;DR

This paper reports a new upper limit on the solar neutrino effective magnetic moment using Borexino Phase-II data, constraining neutrino properties and magnetic moments with high precision.

Contribution

It provides the most stringent upper limit to date on the solar neutrino effective magnetic moment from Borexino data, improving constraints on neutrino magnetic properties.

Findings

No significant deviation in electron recoil spectrum.

Upper limit on effective neutrino magnetic moment: < 2.8×10^{-11} μ_B.

Derived limits for neutrino magnetic moments of flavor states.

Abstract

A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of $\mu_{\nu}^{eff}$ $<$ 2.8$\cdot$10$^{-11}$ $\mu_{B}$ at 90\% c.l. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments.Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magnetic moments matrix for Dirac and Majorana neutrinos, are derived.