Abstract
The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the νμ → ντ channel, the ντ signature being the identification of the τ-lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. Placed in the LNGS, it is exposed to the high-energy long-baseline CERN Neutrino beam to Gran Sasso (CNGS) 730 km away from the neutrino source. The observation of a first ντ candidate event was reported in 2010. In this paper, we discuss the result of the analysis of the data taken during the first two years of operation (2008–2009) underlining the major improvements brought to the analysis chain and to the Monte Carlo simulations. The statistical significance of the one event observed so far is then evaluated to 95%.
ISSN:1367-2630