A study by Borexino shows, for the first time, how the interaction of sub-MeV solar neutrinos in liquid scintillator retains measurable directional information carried by the sub-dominant Cherenkov light component produced in neutrino-electron scatters. Cherenkov light is emitted along the direction of the recoiling electron, and is emitted with a faster profile than scintillation light. The demonstration by Borexino paves the way to the development of future neutrino detectors in which the Cherenkov-to-scintillation light ratio and relative emission timing, measured by fast photodetectors, is engineered to enhance the sensitivity to directional information.
The work appeared in two side-by-side papers in PRL and PRD and was highlighted by the editor with a Physics Synopsis.