Les rencontres de physique de la vallée d'Aoste. Results and perspectives in particle physics. Vol. 5

Several experiments carried out in the last decades with atmospheric and accelerator neutrinos, as well as with solar and reactor neutrinos, contributed to our present understanding of neutrino mixing (see, e.g., Strumia and Vissani [arXiv:hep-ph/0606054] for a review). The OPERA experiment aims at measuring the first detection of neutrino oscillation in appearance mode through the detection of ντ in an almost pure νμ beam produced at CERN SPS (CNGS), 730 km far from the detector. The ντ appearance signal is detected through the measurement of the decay daughter particles of the τ lepton produced in CC ντ interactions. Since the short-lived tau; particle has, at the energy of the beam, an average decay length of about ∼ 1mm, a micrometric detection resolution is needed. Runs with CNGS neutrinos were succesfully carried out in 2007 and 2008 with the detector fully operational with its related facilities for the emulsion handling and analysis. After a brief description of the beam and of the experimental setup we report on the collection, reconstruction and analysis procedures of first samples of neutrino interaction events.