The study of solar neutrinos and of non-standard neutrino interactions with Borexino

The Borexino liquid scintillator neutrino observatory has a unique capability to perform high-precision solar neutrino observations thanks to its exceptional radiopurity and good energy resolution (5% at 1 MeV). A comprehensive study of the pp-chain neutrinos was presented that includes the direct measurements of 7Be, pp and pep neutrino fluxes with the highest precision ever achieved (down to 2.8% in the 7Be component), the 8B with the lowest energy threshold, the best limit on CNO neutrinos and the first Borexino limit on hep neutrinos. These results are important to validate the MSW-LMA oscillation paradigm across the full solar energy range and to exclude possible Non-Standard neutrino Interactions (NSIs). In particular the effects of neutrino-flavor-diagonal Neutral-Current (NC) interactions that modify the νee and ντe couplings while preserving their chiral and flavor structures, have been investigated. At detection, the shape of the electron-recoil spectrum is affected by changes in the νee and ντe couplings, quantified by the parameters εL/Re and εL/Rτ. New bounds to all four parameters were obtained, quite stringent compared to the global ones. In particular, the best constraint to-date on εLe was achieved. A comprehensive summary of all the recent results on solar neutrinos from Borexino is reported in the present paper. (BOREXINO Collaboration)