First Alignment of the Complete CMS Tracker

TL;DR

This paper reports the initial alignment results of the full CMS Tracker using cosmic ray data, achieving micrometer precision in module positioning to enhance track-parameter resolution for future proton collision analyses.

Contribution

It presents the first complete alignment of the CMS Tracker modules using cosmic data and advanced algorithms, addressing the challenges of an all-silicon detector system.

Findings

Achieved micrometer-level alignment precision

Validated track parameter resolution with data-driven methods

Provided outlook for improved tracking with proton collisions

Abstract

This conference proceeding presents the first results of the full CMS Tracker alignment based on several million reconstructed tracks from the cosmic data taken during the commissioning runs with the detector in its final position and magnetic field present. The all-silicon design of the CMS Tracker poses new challenges in aligning a complex system with 15\,148 silicon strip and 1440 silicon pixel modules. For optimal track-parameter resolution, the position and orientation of its modules need to be determined with a precision of about one micrometer. The modules, well illuminated by cosmic ray particles, were aligned using two track-based alignment algorithms in sequence in combination with survey measurements. The resolution in all five track parameters is controlled with data-driven validation of the track parameter measurements near the interaction region, and tested against prediction with detailed detector simulation. An outlook for the expected tracking performance with the first proton collisions is given.