Pinning down neutrino oscillation parameters in the 2\u20133 sector with a magnetised atmospheric neutrino detector: a new study

Abstract

We determine the sensitivity to neutrino oscillation parameters from a study of atmospheric neutrinos in a magnetised detector such as the ICAL at the proposed India-based Neutrino Observatory. In such a detector, which can separately count nu _mu and overline{nu }_mu -induced events, the relatively smaller (about 5%) uncertainties on the neutrino–antineutrino flux ratios translate to a constraint in the chi ^2 analysis that results in a significant improvement in the precision with which neutrino oscillation parameters such as sin ^2theta _{23} can be determined. Such an effect is unique to all magnetisable detectors and constitutes a great advantage in determining neutrino oscillation parameters using such detectors. Such a study has been performed for the first time here. Along with an increase in the kinematic range compared to earlier analyses, this results in sensitivities to oscillation parameters in the 2–3 sector that are comparable to or better than those from accelerator experiments where the fluxes are significantly higher. For example, the 1sigma precisions on sin ^2theta _{23} and |Delta {m^2_{32(31)}}| achievable for 500 kton year exposure of ICAL are {sim }9 and {sim }2.5%, respectively, for both normal and inverted hierarchies. The mass hierarchy sensitivity achievable with this combination when the true hierarchy is normal (inverted) for the same exposure is Delta chi ^2approx 8.5 (Delta chi ^2approx 9.5).