Performance of ALICE silicon tracker detector

ALICE (A Large Ion Collider Experiment) is the LHC experiment devoted to the study of the strong interacting matter created in heavy-ion collisions. The ALICE Inner Tracking System (ITS) consists of six layers of silicon detectors exploiting three different technologies: pixel, drift and strip (from inside to outside). It covers the central pseudorapidity range, j h j < 0 : 9, and its distance from the beam line ranges from r = 3 : 9 cm for the innermost pixel layer up to r = 43 cm for the outermost strip layer. The main tasks of the ITS are to reconstruct the primary and secondary vertices, to track and identify charged particles with a low- p T cutoff and to improve the momentum resolution at high p T . During the operations, the ITS has demonstrated its tracking and vertexing capabilities, which are in excellent agreement with the design values. In these proceedings, after a brief description of the features of the system, the performance during the first three years of data taking at LHC will be presented.