Alignment of the CMS Muon System with Cosmic-Ray and Beam-Halo Muons

TL;DR

This paper describes the alignment process of the CMS muon system using cosmic-ray and beam-halo muons, achieving high precision in chamber positioning, which is crucial for accurate muon detection in particle physics experiments.

Contribution

The paper presents a detailed alignment method for the CMS muon system using cosmic-ray and beam-halo muons, with results indicating high positional resolution and potential for further improvements with collision data.

Findings

Achieved 80 micron resolution for superlayer alignment

Achieved 270 micron resolution for endcap chambers

Alignment procedures adaptable for LHC collision muons

Abstract

The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements.