The OPERA Long Baseline Experiment: Status and First Results

OPERA (Oscillation Project with Emulsion tRacking Apparatus) is an international collaboration between Europe and Asia, aiming to give the first direct proof of tau neutrino appearance in a pure muon neutrino beam, in order to validate the hypothesis for atmospheric neutrino oscillations. The first european long baseline neutrino beam called CNGS is produced at CERN and sent in the direction of the Gran Sasso underground laboratory 730 km away, where the OPERA detector is located. Since 2006 the electronic detector part is fully commissioned and running. Cosmic ray events have been recorded on a regular basis and the first neutrino beam events have been observed in the target elements made of very precise emulsion films and lead sheets during the last run in autumn 2007. This paper reviews the status of the detector, the beam performances, the first results from the neutrino event analysis and the prospects.