Atmospheric neutrino oscillation analysis with external constraints in Super-Kamiokande I-IV

TL;DR

This paper analyzes atmospheric neutrino data from Super-Kamiokande I-IV to determine neutrino oscillation parameters and the neutrino mass hierarchy, incorporating external constraints to improve sensitivity and favoring the normal hierarchy.

Contribution

It provides the first combined analysis of atmospheric neutrino data with external constraints to enhance sensitivity to the neutrino mass hierarchy.

Findings

Normal hierarchy favored with 91.5%-94.5% confidence

Confidence intervals for key oscillation parameters are provided

External constraints improve parameter determination

Abstract

An analysis of atmospheric neutrino data from all four run periods of \superk optimized for sensitivity to the neutrino mass hierarchy is presented. Confidence intervals for $\Delta m^2_{32}$, $\sin^2 \theta_{23}$, $\sin^2 \theta_{13}$ and $\delta_{CP}$ are presented for normal neutrino mass hierarchy and inverted neutrino mass hierarchy hypotheses based on atmospheric neutrino data alone. Additional constraints from reactor data on $\theta_{13}$ and from published binned T2K data on muon neutrino disappearance and electron neutrino appearance are added to the atmospheric neutrino fit to give enhanced constraints on the above parameters. Over the range of parameters allowed at 90% confidence level, the normal mass hierarchy is favored by between 91.5% and 94.5% based on the combined result.