OPERA (\emph{O}scillation \emph{P}roject with \emph{E}mulsion t\emph{R}acking
\emph{A}pparatus) is a long-baseline neutrino experiment, designed to provide
the first direct proof of νμ​→ντ​ oscillation in the atmospheric
sector using the \emph{C}ERN \emph{N}eutrinos to \emph{G}ran \emph{S}asso
(CNGS) νμ​ beam. The detector, consisting of a modular target made of
lead - nuclear emulsion units complemented by electronic trackers and muon
spectrometers, has been conceived to select ντ​ charged current
interactions, among all neutrino flavour events, through the observation of the
outcoming tau leptons and subsequent decays. In this paper, the detector, the
event analysis chain and the preliminary results from the first OPERA physics
run are reported.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072