Readiness of the ATLAS Liquid Argon Calorimeter for LHC Collisions

TL;DR

The paper evaluates the performance of the ATLAS liquid argon calorimeter, demonstrating its readiness for LHC collisions through various in situ measurements and calibration methods.

Contribution

It provides a comprehensive in situ performance assessment of the calorimeter, confirming its operational stability and calibration accuracy before LHC collisions.

Findings

Calorimeter operated stably with good timing performance.

Energy resolution's intrinsic constant term verified.

Uniform response along eta measured at percent level.

Abstract

The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.