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

TL;DR

This paper details the alignment procedures for the CMS silicon tracker, achieving micrometer-level precision essential for accurate particle tracking and vertex reconstruction in high-energy physics experiments.

Contribution

It presents a comprehensive alignment method for the CMS silicon tracker, improving detector precision using data from cosmic rays and proton collisions, validated through multiple data-driven techniques.

Findings

Achieved alignment precision of less than 10 microns.

Validated alignment through data-driven studies and simulations.

Enhanced track-parameter resolution for better physics analyses.

Abstract

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.