Performance of the ATLAS Liquid Argon Calorimeter After Three Years of LHC Operation and Plans for a Future Upgrade

The ATLAS experiment is a multi-purpose detector built for analyzing LHC collision data. In July 2012, ATLAS announced the discovery of the Higgs boson, the last undiscovered particle in the Standard Model of particle physics. The ATLAS Liquid Argon (LAr) Calorimeter played a crucial role in the discovery by providing accurate measurements of Higgs final states such as photons, electrons and jets. The LAr detector is a sampling calorimeter consisting of four subsystems: an electromagnetic barrel (EMB), electromagnetic end-caps (EMEC), hadronic end-caps (HEC), and forward calorimeters (FCAL). The liquid argon purity, temperature and time stability remained well above the required levels throughout the data-taking period. Overall the calorimeter performed very well, with over 99% of data it collected in 2012 proton-proton collisions being suitable for physics analysis. In order to maintain good LAr detector performance, several upgrades are currently being implemented and planned.