ALICE silicon tracker alignment and performance

The Inner Tracking System (ITS) is the detector of the ALICE central barrel located closest to the beam axis and it is therefore a key detector for tracking and vertexing performance. It consists of six cylindrical layers of silicon detectors with three different technologies: two layers each of pixel, drift and strip detectors. We present here the results obtained for the ITS alignment using charged tracks from cosmic rays and the first pp collision data, including the validation of survey measurements, the analysis of the track-to-track and point-to-track residuals as a tool for determining the residual misalignment and monitoring the global alignment of the system. A first look at the track impact parameter resolution extracted from the data is also presented.