Evidence for $\nu_\mu \to \nu_\tau$ appearance in the CNGS neutrino beam   with the OPERA experiment
  The OPERA experiment is designed to search for $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillations in appearance mode i.e. through the direct observation of the $\tau$ lepton in $\nu_{\tau}$ charged current interactions. The experiment has taken data for five years, since 2008, with the CERN Neutrino to Gran Sasso beam. Previously, two $\nu_{\tau}$ candidates with a $\tau$ decaying into hadrons were observed in a sub-sample of data of the 2008-2011 runs. Here we report the observation of a third $\nu_\tau$ candidate in the $\tau^-\to\mu^-$ decay channel coming from the analysis of a sub-sample of the 2012 run. Taking into account the estimated background, the absence of $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillations is excluded at the 3.4 $\sigma$ level. 
N. Agafonova, A. Aleksandrov, A. Anokhina, S. Aoki, A. Ariga, T.   Ariga, T. Asada, D. Autiero, A. Ben Dhahbi, A. Badertsche...
hep-ex physics.ins-det