Electron/Photon Reconstruction Performance with the ATLAS Detector

The calibration of electromagnetic clusters is one of the key issues of ATLAS (and the LHC) in 2007. The cluster algorithm starting from electronically calibrated calorimeter cells will be described. Local position and local energy variations are corrected for. As a last step, longitudinal weights are applied to correct for energy loss upstream of the calorimeter. Strongly influenced by testbeam studies, the new longitudinal weighting optimizes simultaneously energy resolution and linearity. Methods to derive the final calibration parameters from the physics events have been developed. The electron and photon identification methods and their performance will then be discussed.