The CMS tracker calibration workflow: experience with cosmic ray data.

During the second part of 2008 a CMS commissioning was performed with the acquisition of cosmic events in global runs. Cosmic rays detected in the muon chambers were used to trigger the readout of all CMS subdetectors in the general data acquisition system. A total of about 300M of tracks were collected by the CMS Muon Chambers with a 3.8T magnetic field produced by the CMS superconducting solenoid, 6M of which pointing to the tracker region and reconstructed by the Si-Strip tracker (SST) detectors. Other 1M of cosmic tracks were collected with the magnetic field off. Using the cosmic data available it was possible to validate the performances of the CMS tracker calibration workflows. In this paper the adopted calibration workflow is described. In particular, the three main calibration workflows requested for the low level reconstruction of the SST, i.e. gain calibration, Lorentz angle calibration and bad components identification, are described. The results obtained using cosmic tracks for these three calibration workflows are also presented.