Search for u_{tau} interactions with the nuclear emulsion films of the OPERA experiment

The OPERA experiment aims at measuring the u_{mu} -> u_{tau} oscillation through the u_{tau} appearance in an almost pure u_{mu} beam (CNGS). For the direct identification of the short-lived {tau} lepton, produced in u_{tau} CC interactions, a micrometric detection resolution is needed. Therefore the OPERA detector makes use of nuclear emulsion films, the highest spatial resolution tracking device, combined with lead plates in an emulsion cloud chamber (ECC) structure called brick. In this paper the nuclear emulsion analysis chain is reported; the strategy and the algorithms set up will be described together with their performances.