Аннотация:The OPERA experiment was designed to search for νμ→ντ oscillations in appearance mode, i.e., by detecting the τ leptons produced in charged current ντ interactions. The experiment took data from 2008 to 2012 in the CERN Neutrinos to Gran Sasso beam. The observation of the νμ→ντ appearance, achieved with four candidate events in a subsample of the data, was previously reported. In this Letter, a fifth ντ candidate event, found in an enlarged data sample, is described. Together with a further reduction of the expected background, the candidate events detected so far allow us to assess the discovery of νμ→ντ oscillations in appearance mode with a significance larger than 5σ.
