Hunting potassium geoneutrinos with liquid scintillator Cherenkov neutrino detectors

The research of geoneutrino is a new interdisciplinary subject of particle experiments and geo-science. Potassium-40 (${}^{\text{40}}$K) decays contribute roughly 1/3 of the radiogenic heat of the Earth, but it is still missing from the experimental observation. Solar neutrino experiments with liquid scintillators have observed uranium and thorium geoneutrinos and are the most promising in the low-background neutrino detection. In this article, we present the new concept of using liquid-scintillator Cherenkov detectors to detect the neutrino-electron elastic scattering process of ${}^{\text{40}}$K geoneutrinos. Liquid-scintillator Cherenkov detectors using a slow liquid scintillator can achieve this goal with both energy and direction measurements for charged particles. Given the directionality, we can significantly suppress the dominant intrinsic background originating from solar neutrinos in conventional liquid-scintillator detectors. We simulated the solar- and geo-neutrino scatterings in the slow liquid scintillator detector, and implemented energy and directional reconstructions for the recoiling electrons. We found that ${}^{\text{40}}$K geoneutrinos can be detected with three standard deviation accuracy in a kiloton-scale detector.