Super-PINGU for measurement of the leptonic CP-phase with atmospheric neutrinos

Abstract: We explore a possibility to measure the CP-violating phase δ using multimegaton scale ice or water Cherenkov detectors with low, (0.2-1) GeV, energy threshold assuming that the neutrino mass hierarchy is identified. We elaborate the relevant theoretical and phenomenological aspects of this possibility. The distributions of the ν_μ (track) and ν_e (cascade) events in the neutrino energy and zenith angle (E_ν − θ_z) plane have been computed for different values of δ. We study properties and distinguishability of the distributions before and after smearing over the neutrino energy and zenith angle. The CP-violation effects are not washed out by smearing, and furthermore, the sensitivity to δ increases with decrease of the energy threshold. The ν_e events contribute to the CP-sensitivity as much as the ν_μ events. While sensitivity of PINGU to δ is low, we find that future possible upgrade, Super-PINGU, with few megaton effective volume at (0.5-1) GeV and e.g. after 4 years of exposure will be able to disentangle values of δ = π/2, π, 3π/2 from δ = 0 with “distinguishability” (∼ significance in σ’s) S_σ ^tot = (3 − 8), (6 − 14), (3 − 8) correspondingly. Here the intervals of S^σot are due to various uncertainties of detection of the low energy events, especially the flavor identification, systematics, etc. Super-PINGU can be used simultaneously for the proton decay searches.