Large-energy single hits at JUNO from atmospheric neutrinos and dark matter

Abstract

Large liquid scintillator detectors, such as JUNO, present a new opportunity to study neutral current events from the low-energy end of the atmospheric neutrinos, and possible new physics signals due to light dark matter. We carefully study the possibility of detecting ``large-energy singles'' (LES), i.e., events with visible scintillation energy $>15\text{ }\text{ }\mathrm{MeV}$, but no other associated tags. For an effective exposure of $20\text{ }\text{ }\mathrm{kton}\ensuremath{-}\mathrm{yr}$ and considering only Standard Model physics, we expect the LES sample to contain $\ensuremath{\sim}40$ events from scattering on free protons and $\ensuremath{\sim}108$ events from interaction with carbon, from neutral-current interactions of atmospheric neutrinos. Backgrounds, largely due to $\ensuremath{\beta}$ decays of cosmogenic isotopes, are shown to be significant only below 15 MeV visible energy. The LES sample at JUNO can competitively probe a variety of new physics scenarios, such as boosted dark matter and annihilation of galactic dark matter to sterile neutrinos.