Electron Reconstruction and Identification with the ATLAS Detector

The understanding of the reconstruction of electrons will be one of the key issues at the start-up of data-taking with the ATLAS experiment at the LHC in 2009. The energy measurement of electrons is based on the electromagnetic calorimetry over most of the relevant energy range (5 GeV to a few TeV). The electromagnetic calorimeter cluster algorithm starts from electronically calibrated calorimeter cells where local position and energy variations are then corrected for. A refined calibration procedure, developed and validated over years of test-beam data-taking and analysis, strives to identify all sources of energy losses upstream of the calorimeter and outside the cluster and corrects for them one by one (using Monte-Carlo). To achieve this, the material in front of the calorimeter will have to be mapped out precisely using other methods. The electron identification is based on the shower shapes in the calorimeter and relies on the tracker and combined tracker/calo information to achieve the required rejection of 10^5 against QCD jets for a reasonably clean inclusive electron spectrum in the moderate pT region of 10 to 50 GeV. The required rejection factor is closer to a thousand per jet to cleanly extract the signal expected from di-electron resonances in the TeV mass range. The electron calibration and identification methods as well as their performance will be discussed herein.