2019/09/05 by M. Agostini, Agostini, M., Simon Appel +172 · 1 citation
Physics and Astronomy · #Neutrino Physics Research #Dark Matter and Cosmic Phenomena #Astrophysics and Cosmic Phenomena
paper · pdf · doi:10.48550/arxiv.1909.02422
We report on searches for neutrinos and antineutrinos from astrophysical sources performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. Electron antineutrinos (νe) are detected in an organic liquid scintillator through the inverse β-decay reaction. In the present work we set model-independent upper limits in the energy range 1.8-16.8 MeV on neutrino fluxes from unknown sources that improve our previous results, on average, by a factor 2.5. Using the same data set, we first obtain experimental constraints on the diffuse supernova νe fluxes in the previously unexplored region below 8 MeV. A search for νe in the solar neutrino flux is also presented: the presence of νe would be a manifestation of a non-zero anomalous magnetic moment of the neutrino, making possible its conversion to antineutrinos in the strong magnetic field of the Sun. We obtain a limit for a solar νe flux of 384 cm-2s-1 (90% C.L.), assuming an undistorted solar 8B neutrinos energy spectrum, that corresponds to a transition probability p_ νe → νe 1.8 MeV. At lower energies, by investigating the spectral shape of elastic scattering events, we obtain a new limit on solar 7Be-νe conversion into νe of p_ νe → νe