Abstract:

I will report on the first observation of solar neutrinos in the 1.0 - 1.5 MeV range. This result represents the first experimental evidence for pep solar neutrinos and provides the strongest constraint on the CNO neutrino flux to date, a first step toward high-precision tests of solar neutrino oscillations and the resolution of the solar composition problem. This measurement was made possible by the low radioactive background levels in Borexino and by the adoption of novel data analysis techniques for the suppression of cosmogenic 11C.