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Borexino was a liquid scintillator detector situated underground in the Laboratori Nazionali del Gran Sasso in Italy, officially decommissioned in October 2021. Its successful and renowned physics program covered the study of solar neutrinos program and spans also across geo-neutrinos and neutrino physics. Within its solar program, Borexino successfully measured neutrinos from the fusion processes in the pp chain and CNO cycle. For the detection of pep and CNO neutrinos, an especially important background is formed by the cosmogenic radio-isotope 11C that is produced by muon spallation of 12C nuclei in the scintillator. Given the relatively long lifetime (30 mins) and high rate (30 cpd per 100 ton), specific signal identification is not possible. Borexino developed dedicated veto strategies in the data analysis phase to allow the detection of pep and CNO neutrinos. The results presented so far by Borexino relied upon a Three-Fold Coincidence (TFC) technique that exploits the time and space correlation of muons, spallation neutrons, and radioactive 11C decays. This method has conservative assumptions during critical data-taking periods, such as during a board saturation case or between runs, which causes a loss of data exposure. Therefore, a new algorithm is devised to relax these TFC assumptions and deal with the critical periods by searching for space-time correlated bursts of 11C events produced in cascade by the spallation. In this work, we present the state of the art of the TFC, the new algorithm working, and highlight the performance of their combination to deal with the 11C background. Moreover, this method finds a general application in low radioactivity Borexino-like underground experiments when dealing with any background having a decay time too long to be identified by the triggers. [ABSTRACT FROM AUTHOR]

Important neutrino results came recently from Borexino, a massive, calorimetric liquid scintillator detector installed at the underground Gran Sasso Laboratory. With its unprecedented radiopurity levels achieved in the core of the detection medium, it is the only experiment in operation able to study in real time solar neutrino interactions in the challenging sub-MeV energy region. The recently achieved breakthrough observation of the fundamental pp flux, the precise measurement of the 7Be solar neutrino flux, and the results concerning the pep, 8B and CNO fluxes, together with their physics implications, are described in this work. Moreover, the detector has also provided a clean detection of terrestrial neutrinos, from which they emerge as a new probe of the interior of the Earth. [ABSTRACT FROM AUTHOR]

Cosmogenic 11C is produced in-situ by atmospheric muons and forms the main background for the measurement of solar pep- and CNO-neutrinos. However, FLUKA simulations show that the majority of 11C is accompanied by a free neutron in the final state, thus allowing for an efficient tagging method, the so-called Three-Fold Coincidence technique. The technique and its first applications on Borexino data are presented. [ABSTRACT FROM AUTHOR]