A Measurement of the Tau Neutrino Cross Section in Atmospheric Neutrino Oscillations with Super-Kamiokande

TL;DR

This study measures the tau neutrino cross section and confirms tau neutrino appearance in atmospheric neutrinos using Super-Kamiokande data, providing results consistent with the Standard Model and excluding no-appearance hypotheses.

Contribution

First measurement of the atmospheric tau neutrino cross section and direct observation of tau neutrino appearance with high significance in Super-Kamiokande.

Findings

Tau normalization measured at 1.47±0.32

Tau neutrino appearance excluded with 4.6σ significance

Cross section consistent with Standard Model predictions

Abstract

Using 5,326 days of atmospheric neutrino data, a search for atmospheric tau neutrino appearance has been performed in the Super-Kamiokande experiment. Super-Kamiokande measures the tau normalization to be 1.47$\pm$0.32 under the assumption of normal neutrino hierarchy, relative to the expectation of unity with neutrino oscillation. The result excludes the hypothesis of no-tau-appearance with a significance level of 4.6$\sigma$. The inclusive charged-current tau neutrino cross section averaged by the tau neutrino flux at Super-Kamiokande is measured to be $(0.94\pm0.20)\times 10^{-38}$ cm$^{2}$. The measurement is consistent with the Standard Model prediction, agreeing to within 1.5$\sigma$.