The CMS tracking algorithms and their performances in cosmic ray data

The CMS tracker is the largest silicon detector ever constructed, with about 200 square meters of active area and over 70 million readout channels. The tracker will operate in a very difficult environment, due to the large track multiplicity that will arise from LHC collisions. The amount of material the tracker itself is made of will make the task of track reconstruction at CMS even more challenging. During the 2008 Cosmic Run at Four Tesla (CRAFT) the CMS tracker operated for the first time with the rest of the CMS detectors and about 6 millions cosmic muons were reconstructed. In 2009 the data taking was repeated and this time about 12 millions cosmic muons were reconstructed. With this amount of data it was possible to test the detector performances, to align the detector and to test the CMS track reconstruction algorithms with real cosmic events. In this talk I will present the main algorithms used for track reconstruction at CMS and I will show the results achieved with the cosmic ray data collected by CMS during CRAFT08 and CRAFT09