Discrimination of pp solar neutrinos and ${}^{14}$C double pile-up events in a large-scale LS detector

As a unique probe, precision measurement of $\mathit{\text{pp}}$ solar neutrinos is important for studying the Sun’s energy mechanism, monitoring thermodynamic equilibrium, and studying neutrino oscillation in the vacuum-dominated region. For a large-scale liquid scintillator detector, one bottleneck for $\mathit{\text{pp}}$ solar neutrino detection comes from pile-up events of intrinsic ${}^{14}$C decays. This paper presents a few approaches to discriminate $\mathit{\text{pp}}$ solar neutrinos and ${}^{14}$C pile-up events by considering the difference in their time and spatial distributions. In this work, a Geant4-based Monte Carlo simulation is constructed. Then multivariate analysis and deep learning technology were adopted respectively to investigate the capability of ${}^{14}$C pile-up reduction. As a result, the BDTG model and VGG network showed good performance in discriminating $\mathit{\text{pp}}$ solar neutrinos and ${}^{14}$C double pile-up events. Their signal significance can achieve 10.3 and 15.6 using only one day of statistics. In this case, the signal efficiency is 51.1% for discrimination using the BDTG model when rejecting 99.18% ${}^{14}$C double pile-up events, and the signal efficiency is 42.7% for the case using the VGG network when rejecting 99.81% ${}^{14}$C double pile-up events.