Phys. Rev. D 82, 033006 (2010) [10 pages]
published 5 August 2010
G. Bellini et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek
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Abstract
We report the measurement of ν-e elastic scattering from 8B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.22±0.04(stat)±0.01(syst) cpd/100 t, which corresponds to Φ8BES=2.4±0.4±0.1×106 cm-2 s-1, in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the 8B neutrino flux predicted by the high metallicity standard solar model, the average 8B νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for 7Be and 8B neutrinos as measured by Borexino differ by 1.9σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar νe survival probability Pee between the low-energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.