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Search for low-energy neutrinos from astrophysical sources with Borexino

Agostini, M; Altenmüller, K; Appel, S; Atroshchenko, V; Bagdasarian, Z; Basilico, D; Bellini, G; ... Wojcik, M; + view all (2021) Search for low-energy neutrinos from astrophysical sources with Borexino. Astroparticle Physics , 125 , Article 102509. 10.1016/j.astropartphys.2020.102509.

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Abstract

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 (ν¯_{e}) 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 ν¯_{e} fluxes in the previously unexplored region below 8 MeV. A search for ν¯_{e} in the solar neutrino flux is also presented: the presence of ν¯_{e} 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 ν¯_{e} flux of 384 cm^{–2} s^{–1} (90% C.L.), assuming an undistorted solar {8}^B neutrinos energy spectrum, that corresponds to a transition probability p_{ν}_{e}→ν¯_{e} < 7.2 × 10^{–5} (90% C.L.) for E_{ν¯}_{e} > 1.8 MeV. At lower energies, by investigating the spectral shape of elastic scattering events, we obtain a new limit on solar {7^}Be-ν_{e} conversion into ν¯_{e} of p_{ν}_{e} → ν¯_{e} < 0.14 (90% C.L.) at 0.862 MeV. Last, we investigate solar flares as possible neutrino sources and obtain the strongest up-to-date limits on the fluence of neutrinos of all flavor neutrino below 3–7 MeV. Assuming the neutrino flux to be proportional to the flare's intensity, we exclude an intense solar flare as the cause of the observed excess of events in run 117 of the Cl-Ar Homestake experiment.

Type: Article
Title: Search for low-energy neutrinos from astrophysical sources with Borexino
DOI: 10.1016/j.astropartphys.2020.102509
Publisher version: https://doi.org/10.1016/j.astropartphys.2020.10250...
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
Keywords: Antineutrinos, Neutrinos, Diffuse supernova neutrino background, Supernova relic neutrinos, Solar flares
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10111984
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