Super-Kamiokande atmospheric neutrino results

TL;DR

This paper reports on atmospheric neutrino observations from Super-Kamiokande, confirming muon neutrino oscillations primarily into tau neutrinos, and disfavors sterile neutrino involvement at high confidence.

Contribution

First detailed analysis of atmospheric neutrino oscillations with a large dataset, providing evidence for muon to tau neutrino oscillations and constraining sterile neutrino hypotheses.

Findings

Data well explained by $ u_{} o u_{ au}$ oscillations.

Pure $ u_{} o u_s$ oscillation disfavored at 99% C.L.

Evidence for $ u_{ au}$ appearance at about two sigma level.

Abstract

We present atmospheric neutrino results from a 79 kiloton year (1289 days) exposure of the Super-Kamiokande detector. Our data are well explained by $\nu_{\mu} \to \nu_{\tau}$ 2-flavor oscillations. We have been attempting to discriminate between the possible oscillating partners of the muon neutrino as being either the tau neutrino or the sterile neutrino. Pure $\nu_\mu\to\nu_s$ oscillation is disfavored at 99% C.L.. Moreover, we performed the appearance search for charged current tau neutrino interactions in the upward-going samples. Our data is consistent with $\nu_{\tau}$ appearance at roughly the two-sigma level.