An algorithm for track reconstruction in the large angle spectrometer of the COMPASS experiment

An algorithm is presented for track reconstruction in the large angle spectrometer of a high energy fixed target experiment. Pattern recognition is provided by the association of segments found on both sides of the deflecting magnet within a variable roadwidth tuned to the characteristics of the experimental layout. Curved tracks swept away by the magnet are also searched for in the upstream telescope. The procedure has been tested on various sets of simulated data from the COMPASS experiment at CERN. The obtained track reconstruction efficiency reaches 85% for momenta above 2.5 GeV and is about 50% at 1 GeV, fulfilling one of the basic requirements of this experiment for the analysis of charmed meson decays.