A new approach to identify cosmogenic ¹¹C burst in Borexino

Borexino is a liquid scintillator detector sited underground in the Laboratori Nazionali del Gran Sasso. Its physics program is centred in the study of solar neutrinos, in particular from the Beryllium, pp, pep and CNO fusion reactions. With the start of the phase II, the aim is to improve the pep and CNO results. The background sources are mainly radioisotopes induced by muons in the detector, in particular ¹¹C cosmogenics produced in muon spallation from ¹²C nuclei with emission of neutrons. The physics of this process is not very well understood, therefore carbon isotopes are not easy to predict. The Borexino analysis approach to deal with them, called Three Fold Coincidence (TFC), relies on time and space coincidence of muons, neutrons and ¹¹C, vetoing volumes where those associated signatures occurred. The work presented is a new approach to identify ¹¹C events produced in ''bursts'', i.e. by the same muon, entirely based on their correlations in time and space, without using μ and n signals. This cannot fully substitute the TFC technique, but in combination is expected to reduce the vetoed volumes, increasing the data statistics of the neutrino measurements. Moreover, it might be used to better identify ¹¹C samples to improve the study of the physics of their production.