Borexino is a large volume liquid scintillation neutrino detector located in Laboratori Nazionali del Gran Sasso (Italy). Although its primary goal was the study of low energy solar neutrinos, Borexino has sensitivity to a variety of rare processes in the ~100 keV to a few MeV range due to the unprecedentedly low radioactivity level achieved in the detector, as well as good energy resolution.

This work is dedicated to the search for rare processes related to the two fundamental lepton properties, namely, the electron lifetime and the neutrino magnetic moment, in the Borexino data. The electron lifetime limit has been obtained from the search for a hypothetical decay of an electron to a photon and a neutrino; the expected signal is a monoenergetic photon with the energy equal to half of the electron mass. The neutrino magnetic moment has been studied with two methods, namely, a direct one, by extracting the contribution of the electromagnetic neutrino-electron interaction to the total cross section, and an indirect one, considering the limit on the flux of solar antineutrinos produced via the neutrino interaction with the magnetic field of the Sun. In this talk, we present the results of the search for the aforementioned rare processes obtained by analysing the energy spectra observed in the detector.

(Based on the materials of the candidate dissertation)