Precision measurement of the 7Be solar neutrino flux and its day-night asymmetry with Borexino

Borexino measures the 7Be solar neutrino flux on 740 live days of data-taking to be 46±1.5+1.6−1.5 events/(day · 100 tons) which corresponds to an equivalent unoscillated flux on Earth of (3.11±0.10+0.11−0.10)·109sec −1 cm−2. This result excludes the no-oscillation hypothesis at 5 σ and provides a precise measurement of the survival probability Pee in the vacuum dominated oscillation regime Pee = 0.51±0.07. Borexino also measures the day-night asymmetry of the 7Be neutrino rate with a total error of 1.4% and finds it to be consistent with zero. This result is in agreement with the MSW-LMA hypothesis and disfavours at more than 8.5 σ the so-called LOW region of the oscillation parameter space.