EUROPEAN PHYSICAL JOURNAL C, vol.74, no.8, 2014 (SCI-Expanded)
The OPERA experiment, designed to perform the first observation of nu(mu) -> nu(tau) oscillations in appearance mode through the detection of the tau leptons produced in nu(tau) charged current interactions, has collected data from 2008 to 2012. In the present paper, the procedure developed to detect tau particle decays, occurring over distances of the order of 1 mm from the neutrino interaction point, is described in detail and applied to the search for charmed hadrons, showing similar decay topologies as the tau lepton. In the analysed sample, 50 charm decay candidate events are observed while 54 +/- 4 are expected, proving that the detector performance and the analysis chain applied to neutrino events are well reproduced by the OPERA simulation and thus validating the methods for nu(tau) appearance detection.