Evidence for the Appearance of Atmospheric Tau Neutrinos in Super-Kamiokande

TL;DR

This paper provides evidence for atmospheric tau neutrino appearance in Super-Kamiokande, using a likelihood analysis to detect tau leptons resulting from neutrino oscillations, with results excluding no-appearance at 3.8 sigma.

Contribution

It presents the first significant detection of tau neutrino appearance in atmospheric neutrinos at Super-Kamiokande, confirming neutrino oscillation models with detailed statistical analysis.

Findings

Tau normalization is 1.42 ± 0.35, indicating tau neutrino appearance.

Approximately 180 tau leptons were produced during the data collection period.

No-tau-appearance hypothesis is excluded at 3.8 sigma.

Abstract

Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum likelihood method to search for the appearance of tau leptons resulting from the interactions of oscillation-generated tau neutrinos in the detector. Relative to the expectation of unity, the tau normalization is found to be $1.42 \pm 0.35 \ (stat) {\}^{+0.14}_{-0.12}\ (syst) $ excluding the no-tau-appearance hypothesis, for which the normalization would be zero, at the 3.8$\sigma$ level. We estimate that $180.1 \pm 44.3\ (stat) {\}^{+17.8}_{-15.2}\ (syst)$ tau leptons were produced in the 22.5 kton fiducial volume of the detector by tau neutrinos during the 2806 day running period. In future analyses, this large sample of selected tau events will allow the study of charged current tau neutrino interaction physics with oscillation produced tau neutrinos.