Paper detail

Alignment of the CMS Silicon Tracker -- and how to improve detectors in the future

The complex system of the CMS all-silicon Tracker, with 15\,148 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. The alignment of pixels modules is crucial for the analyses requiring a precise vertex reconstruction. The aligned geometry is based on the analysis of several million reconstructed tracks recorded during the commissioning of the CMS experiment, both with cosmic rays and with the first proton-proton collisions. Statistical precision of the alignment of the module with respect to the particle trajectories to less than 10 microns has been achieved. The results have been validated by several data-driven studies (track fit self-consistency, track residuals in overlapping module regions, and track parameter resolution) and compared with predictions obtained from a detailed detector simulation.