Measuring Oscillations with A Million Atmospheric Neutrinos

TL;DR

This paper evaluates the potential of atmospheric neutrino experiments to improve measurements of neutrino oscillation parameters, including mass ordering and CP violation, through combined analysis of current and upcoming detectors.

Contribution

It introduces a comprehensive simulation and systematic uncertainty analysis for multiple atmospheric neutrino experiments, demonstrating their combined sensitivity to key neutrino properties.

Findings

Joint analysis can determine the neutrino mass ordering above 5σ by 2030.

Atmospheric neutrino data can independently constrain θ13 and δCP.

Combined measurements improve sensitivity beyond individual experiment capabilities.

Abstract

After two decades of measurements, neutrino physics is now advancing into the precision era. Withthe long-baseline experiments designed to tackle current open questions, a new query arises: can atmospheric neutrino experiments also play a role? To that end, we analyze the expected sensitivity of current and near-future water(ice)-Cherenkov atmospheric neutrino experiments in the context of standard three-flavor neutrino oscillations. In this first in depth combined atmospheric neutrino analysis, we analyze the current shared systematic uncertainties arising from the common flux and neutrino-water interactions. We then implement the systematic uncertainties of each experiment in detail and develop the atmospheric neutrino simulations for Super-Kamiokande, with and without neutron-tagging capabilities, IceCube Upgrade, ORCA, and Hyper-Kamiokande detectors. We carefully review the synergies and features of these experiments to examine the potential of a joint analysis of these atmospheric neutrino data in resolving the $\theta_{23}$ octant at 99% confidence level, and determining the neutrino mass ordering above 5$\sigma$ by 2030. Additionally, we assess the capability to constrain $\theta_{13}$ and the CP -violating phase ($\delta_{CP}$) in the leptonic sector independently from reactor and accelerator neutrino data. A combination of the atmospheric neutrino measurements will enhance the sensitivity to a greater extent than the simple sum of individual experiment results reaching more than 3$\sigma$ for some values of $\delta_{CP}$ . These results will provide vital information for next-generation accelerator neutrino oscillation experiments such as DUNE and Hyper-Kamiokande.