Alignment of the ATLAS barrel muon spectrometer

TL;DR

This paper discusses the alignment procedures of the ATLAS muon spectrometer, crucial for accurate high-energy muon measurements at the LHC, using optical, cosmic ray, and collision track techniques.

Contribution

It presents the development and results of multiple alignment methods to achieve 50-micron precision for high-energy muon detection.

Findings

Alignment accuracy of 50 microns achieved

Optical, cosmic ray, and collision track methods complement each other

Improved momentum resolution for 1 TeV muons

Abstract

The muon spectrometer of the ATLAS experiment is one of the largest detectors ever built. At the LHC, new physics signs could appear through high momentun muons (1 TeV). Identification and precise momentum measurement of such muons are two of the main challenges of the ATLAS muon spectrometer. In order to get a good resolution for high energy muons (i.e. 10% at 1 TeV), the accuracy on the alignment of precision chambers must be of the order of 50 microns. Several procedures have been developed to reach such a precision. This document describes complementary techniques used to align the muon sub-detectors, and their results : the optical system, the muon cosmic rays and the straight tracks coming from collisions.