Improved measurement of 8B solar neutrinos with 1.5 kt ⋅ y of Borexino exposure

We report on an improved measurement of the 8 B solar neutrino interaction rate with the Borexino experiment at the Laboratori Nazionali del Gran Sasso. Neutrinos are detected via their elastic scattering on electrons in a large volume of liquid scintillator. The measured rate of scattered electrons above 3 MeV of energy is ... cpd/100 t, which corresponds to an observed solar neutrino flux assuming no neutrino flavor conversion of ... × 106 cm−2 s−1. This measurement exploits the active volume of the detector in almost its entirety for the first time, and takes advantage of a reduced radioactive background following the 2011 scintillator purification campaign and of novel analysis tools providing a more precise modeling of the background. Additionally, we set a new limit on the interaction rate of solar hep neutrinos, searched via their elastic scattering on electrons as well as their neutral current-mediated inelastic scattering on carbon, 12C (ν, ν′)12C ∗ (Eγ = 15.1 MeV). (ProQuest: ... denotes formula omitted.)