200 days of Borexino data

Borexino is a large-volume liquid scintillator detector placed in the underground halls of the Laboratori Nazionali del Gran Sasso in Italy. After several years of construction, data taking started in May 2007, providing immediately incontrovertible evidence of the unprecedented radiopurity of the target mass. Here we report on the newest Borexino results obtained with about 200 days of data. Borexino provides the first direct measurement of the solar neutrino survival probability in both vacuum-dominated and matter-enhanced regions provided by a single experiment. The interaction rate of the 0.862 MeV 7 Be solar neutrinos is found to be 49 ± 3 stat ± 4 sys counts/(day⋅100 tons), in agreement with the oscillation hypothesis in the MSW Large Mixing Angle scenario. The first real-time measurement of the 8 B solar neutrinos above 2.8 MeV provides interaction rate of 0.26 ± 0.04 stat ± 0.02 sys counts/(day⋅100 tons). These measurements improve the experimental determination of the flux of the pp and CNO solar neutrinos, and the limit on the effective magnetic moment using solar neutrinos.