Study of the electron → photon misidentification rate in the ATLAS detector

In this thesis, the misidentification of electrons as photons (fake rate) is investigated using the first 7 TeV data of the ATLAS detector at the CERN Large Hadron Collider. A method for the measurement of the fake rate in data, using pure electrons from the Z0 → e+e− decay, called tag-and-probe, is presented. The results are studied as functions of kinematic variables in order to show effects on the detector performance. A cross check with a so-called truth-matching method in Monte Carlo is applied. In addition, the fake rate for Gauge Mediated Supersymmetry Breaking events is estimated and compared with Z0 → e+e− studies.