AbstractCosmogenic radio-nuclei are an important source of background for low-energy neutrino experiments. In Borexino, cosmogenic $$^{11}$$
11
C decays outnumber solar pep and CNO neutrino events by about ten to one. In order to extract the flux of these two neutrino species, a highly efficient identification of this background is mandatory. We present here the details of the most consolidated strategy, used throughout Borexino solar neutrino measurements. It hinges upon finding the space-time correlations between $$^{11}$$
11
C decays, the preceding parent muons and the accompanying neutrons. This article describes the working principles and evaluates the performance of this Three-Fold Coincidence (TFC) technique in its two current implementations: a hard-cut and a likelihood-based approach. Both show stable performances throughout Borexino Phases II (2012–2016) and III (2016–2020) data sets, with a $$^{11}$$
11
C tagging efficiency of $$\sim 90$$
∼
90
% and $$\sim $$
∼
63–66 % of the exposure surviving the tagging. We present also a novel technique that targets specifically $$^{11}$$
11
C produced in high-multiplicity during major spallation events. Such $$^{11}$$
11
C appear as a burst of events, whose space-time correlation can be exploited. Burst identification can be combined with the TFC to obtain about the same tagging efficiency of $$\sim 90\%$$
∼
90
%
but with a higher fraction of the exposure surviving, in the range of $$\sim $$
∼
66–68 %.
Studies of prototype CsI(Tl) crystal scintillators for low-energy neutrino experiments
