  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 25 solar
masses, we find that if the electron antineutrino signals from such a star can
be predicted precisely and the star is within ~440-880 pc, the number of events
of electron antineutrino captures on protons 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 electron neutrino and
antineutrino signals from Betelgeuse. This method is feasible if the cosmogenic
background for neutrino-electron 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.
