Observation of nu_tau appearance in the CNGS beam with the OPERA experiment

TL;DR

The OPERA experiment observed a fourth tau neutrino candidate event, providing strong evidence (4.2 sigma significance) for nu_mu to nu_tau oscillations through direct detection of tau leptons.

Contribution

This paper reports the first observation of a fourth nu_tau candidate event, strengthening the evidence for neutrino oscillations with a significance of 4.2 sigma.

Findings

Detection of a fourth nu_tau candidate event.

Establishment of nu_mu to nu_tau oscillations at 4.2 sigma significance.

Confirmation of neutrino oscillation phenomena.

Abstract

The OPERA experiment is searching for nu_mu -> nu_tau oscillations in appearance mode i.e. via the direct detection of tau leptons in nu_tau charged current interactions. The evidence of nu_mu -> nu_tau appearance has been previously reported with three nu_tau candidate events using a sub-sample of data from the 2008-2012 runs. We report here a fourth nu_tau candidate event, with the tau decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analysed events and the low background, nu_mu -> nu_tau oscillations are established with a significance of 4.2sigma.