The LHC and the ATLAS Experiment

Abstract

The analysis in this book has been performed using the data collected with the ATLAS detector at the Large Hadron Collider (LHC) in 2012. This chapter describes some technical details of the LHC and the ATLAS detector. The LHC is the proton-proton collider at CERN. It was operated at the world-highest center-of-mass energy of \(8\,{\mathrm { TeV}}\) and maximum instantaneous luminosity of \(0.7\times 10^{34}\,{\mathrm { cm}}^{-2}\mathrm{s}^{-1}\) in 2012. The ATLAS detector is a multi-purpose detector at the LHC, which consists of inner detectors, electromagnetic and hadronic calorimeters and muon spectrometers. Taking a combination of signals at each sub-detector, secondary particles produced in proton-proton collisions can be identified. All of events produced in proton-proton collisions with approximately 1 GHz of event rate cannot be recorded due to the limit to computer facilities. Therefore, tight event selections have to be applied using online trigger system during the data taking. To collect rare signals against the large amount of background, ATLAS adapts the signature-base trigger system using electron, muon, hadron jets, missing transverse energy and so on. To understand performances of the detector and the trigger system is very important for physics analyses, which are discussed in Chaps. 3 and 4.