Presupernova neutrino signals as potential probes of neutrino mass hierarchy

Abstract

We assess the potential of using presupernova neutrino signals at the Jiangmen Underground Neutrino Observatory (JUNO) to probe the yet-unknown neutrino mass hierarchy. Using models for stars of 12, 15, 20, and 25M⊙, we find that if the ν¯e signals from such a star can be predicted precisely and the star is within ≈440–880 pc, the number of ν¯e+p→n+e+ events detected within one day of its explosion allows to determine the hierarchy at the ≳95% confidence level. For determination at this level using such signals from Betelgeuse, which is at a distance of ≈222 pc, the uncertainty in the predicted number of signals needs to be ≲14–30%. In view of more realistic uncertainties, we discuss and advocate a model-independent determination using both νe and ν¯e signals from Betelgeuse. This method is feasible if the cosmogenic background for ν-e scattering events can be reduced by a factor of ∼2.5–10 from the current estimate. Such reduction might be achieved by using coincidence of the background events, the exploration of which for JUNO is highly desirable.