The OPERA long baseline neutrino experiment: Status and first results

OPERA (Oscillation Project with Emulsion tRacking Apparatus)1 is an international collaboration (Europe-Asia). It aims to give the first direct proof of the νµ → ντ atmospheric oscillation hypothesis, by searching for a ντ appearance at Gran Sasso laboratory in a νµ beam produced at CERN 730 km away. Electronic detectors have been fully commissioned and tested with the first neutrino beam run in 2006, and the full target is expected for summer 2008. OPERA started its neutrino data taking in October 2007, and neutrino interactions have already been reconstructed in the target.