First real time detection of 7Be solar neutrinos by Borexino

This Letter reports a direct measurement of the Be-7 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 Be-7 neutrinos is 47 +/- 7(stat) +/- 12(sys) counts/(day . 100 ton), consistent with predictions of Standard Solar Models and neutrino oscillations with LMA-MSW parameters. (c) 2007 Elsevier B.V. All rights reserved.