Alignment of the CMS Silicon Tracker during Commissioning with Cosmic Rays

TL;DR

This paper details the precise alignment of the CMS silicon tracker using cosmic ray data, achieving micron-level accuracy and validating the alignment through multiple methods to ensure optimal detector performance.

Contribution

It presents a comprehensive alignment procedure for the CMS silicon tracker using cosmic rays and optical surveys, achieving high precision and validation against simulations.

Findings

Module positions determined with 3-14 micron RMS accuracy

Track parameter resolutions close to design specifications

Alignment validated by multiple independent methods

Abstract

The CMS silicon tracker, consisting of 1440 silicon pixel and 15148 silicon strip detector modules, has been aligned using more than three million cosmic ray charged particles, with additional information from optical surveys. The positions of the modules were determined with respect to cosmic ray trajectories to a precision of 3-4 microns RMS in the barrel and 3-14 microns RMS in the endcap in the most sensitive coordinate. The results have been validated by several methods, including the laser alignment system, and compared with predictions obtained from simulation. Correlated systematic effects have been investigated. The track parameter resolutions obtained with this alignment are close to the design performance.