Pinning down neutrino oscillation parameters in the 2-3 sector with a mgnetised atmospheric neutrino detector: a new study

TL;DR

This study demonstrates that a magnetised atmospheric neutrino detector like ICAL can precisely measure neutrino oscillation parameters, especially in the 2-3 sector, outperforming some accelerator experiments due to its ability to distinguish neutrino from antineutrino events.

Contribution

First analysis showing how magnetised detectors improve neutrino oscillation parameter precision by separately counting neutrino and antineutrino events.

Findings

Achieves ~9% precision on  in  sector.

Attains .5% sensitivity to mass hierarchy.

Provides comparable or better sensitivities than accelerator experiments.

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 that can {\em separately} count $\nu_\mu$ and $\overline{\nu}_\mu$-induced events, the relatively smaller (about 5\%) uncertainties on the neutrino--anti-neutrino 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 $\sin^2\theta_{23}$ 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 $1\sigma$ precisions on $\sin^2\theta_{23}$ and $|\Delta{m^2_{32(31)}}|$ achievable for 500 kTon yr exposure of ICAL are $\sim9\%$ and $\sim2.5\%$ 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 $\Delta\chi^2\approx8.5$ ($\Delta\chi^2\approx9.5$).