Solar neutrino physics with BOREXINO i

Abstract

Borexino is a large-volume liquid scintillator detector installed in the underground halls of the Laboratori Nazionali del Gran Sasso in Italy. After several years of construction, data taking started in May 2007. The Borexino phase I ended after about three years of data taking. Borexino provided the first real time measurement of the 7Be solar neutrino interaction rate with accuracy better than 5% and confirmed the absence of its day-night asymmetry with 1.4% precision. This latter Borexino results alone rejects the LOW region of solar neutrino oscillation parameters at more than 8.5 σ C.L. Combined with the other solar neutrino data, Borexino measurements isolate the MSW{LMA solution of neutrino oscillations with-out assuming CPT invariance in the neutrino sector. Borexino has also directly observed solar neutrinos in the 1.0-1.5 MeV energy range, leading to the first direct evidence of the pep solar neutrino signal and the strongest constraint of the CNO solar neutrino ux up to date. Borexino provided the measurement of the solar 8B neutrino rate with 3 MeV energy threshold.