Alignment of the CMS Silicon Tracker

Abstract

The complex system of the CMS all-silicon tracker, with 15148 silicon strip and 1440 silicon pixel modules, requires sophisticated alignment procedures. In order to achieve an optimal track-parameter resolution, the position and orientation of its modules need to be determined with a precision of few micrometers. Several developments of computing and data analysis have been carried out for reaching these performances. Novel tracking tools have been implemented in the alignment algorithms. Special work flows are used for a balanced statistical treatment of the data in order to fully exploit the wide range of physics candles at the LHC that can be exploited by the alignment.We present results of the alignment of the full tracker, in its final position, used for the reconstruction of the first collisions recorded by the CMS experiment. Validation tools are used for checking the quality of the final geometries: the quantities monitored span from the basic track quantities to physics resonances. The geometry has been systematically monitored in the different periods of operation of the CMS detector.