Determinazione delle Prestazioni del Sistema Tracciante di ATLAS con i Primi Dati

The ATLAS Inner Detector is a charged particle tracking system built on three subdetectors: silicon detectors, Pixel and SCT, are complemented with the Transition Radiation Tracker. They provide high precision measurements with fine granularity. The performance of the track reconstruction and the resolution on track parameters are studied in detail with the first data. This study is essential for all physics analysis and for the understanding of the detector during the commissioning phase. In particular, tracking allows to discriminate charged particles sign and to determine their momentum. Furthermore it allows to reconstruct primary vertices of interactions and to identify, through secondary vertices, particles with an average life long enough to cover a significant path within detector.