Probing Leptonic δ<inf>CP</inf> Using Low Energy Atmospheric Neutrinos

The possibility of probing leptonic δCP via oscillations of low energy atmospheric neutrinos is explored. The measurement of δCP is not very easy if the hierarchy of neutrino masses is unknown. Dedicated accelerator long baseline neutrino experiments like DUNE can determine δCP without ambiguity with hierarchy. But low energy atmospheric neutrino events also can be used to determine δCP independent of neutrino mass hierarchy in the energy range 0.1–1.5 GeV. This is also important since the atmospheric neutrino flux peaks in the low energy region and hence will provide a significant number of events for the study. A simple analytical derivation is used to show how the δCP sensitivity arises and what the relevant energies and baselines are. Though the νe and ν¯e events are mainly sensitive to δCP, we also show that in the low energy region, even the νμ and ν¯μ events can contribute to δCP.