First real time detection of 7Be solar neutrinos by Borexino

This Letter reports a direct measurement of the 7Be solar neutrino signal rate performed with the Borexino low background liquid scintillator detector at the Laboratori Nazionali del Gran Sasso. This is the first real-time spectral measurement of sub-MeV solar neutrinos. The result for 0.862 MeV 7Be neutrinos is 47±7stat±12sys47±7stat±12sys counts/(day ⋅ 100 ton), consistent with predictions of Standard Solar Models and neutrino oscillations with LMA-MSW parameters.