New results on solar neutrino fluxes from 192 days of Borexino data

TL;DR

This paper presents the first direct measurement of ^7Be solar neutrino fluxes using Borexino data, confirming neutrino oscillations at a 4-sigma level and refining solar neutrino flux estimates.

Contribution

It provides the first direct measurement of the survival probability of solar neutrinos in the transition oscillation region, improving flux and magnetic moment limits.

Findings

Interaction rate of ^7Be neutrinos measured as 49+-3(stat)+-4(syst) counts/(day * 100ton)

No-oscillation hypothesis is inconsistent at 4 sigma

Enhanced understanding of solar neutrino fluxes and neutrino properties

Abstract

We report the direct measurement of the ^7Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV ^7Be neutrinos is 49+-3(stat)+-4(syst) counts/(day * 100ton). The hypothesis of no oscillation for ^7Be solar neutrinos is inconsistent with our measurement at the 4sigma level. Our result is the first direct measurement of the survival probability for solar nu_e in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of ^7Be, pp, and CNO solar nu_e, and the limit on the magnetic moment of neutrinos.