Discriminating between nu_mu <-> nu_tau and nu_mu <-> nu_sterile in atmospheric nu_mu oscillations with the Super-Kamiokande detector

TL;DR

This paper uses the Super-Kamiokande detector to differentiate between muon neutrino oscillations into tau neutrinos or sterile neutrinos, employing three methods that collectively favor tau neutrino oscillations.

Contribution

The study introduces three distinct techniques to distinguish between nu_tau and nu_s oscillations, providing strong evidence for nu_mu <-> nu_tau oscillations in atmospheric neutrinos.

Findings

Matter effects suppress nu_s oscillations at high energy.

Neutral-current interaction rates are reduced if oscillations involve sterile neutrinos.

Tau appearance is observed, confirming nu_tau involvement.

Abstract

A strong body of evidence now exists for atmospheric nu_mu disappearance oscillations. Such disappearance could be explained by oscillations to either nu_tau or a ``sterile'' neutrino (nu_s). Super-Kamiokande uses three different methods to distinguish between these two scenarios. First, matter effects would suppress the nu_mu <-> nu_s oscillation amplitude at high energy. Second, oscillation to nu_s would reduce the overall neutral-current neutrino interaction rate. Third, the smoking gun of nu_mu <-> nu_tau oscillations would be the observation of tau appearance resulting from charged-current nu_tau interactions. The results of these three techniques are presented, which strongly favor nu_mu <-> nu_tau oscillations over nu_mu <-> nu_s.