Electron/jet separation with DC1 data

Results on the single electron reconstruction efficiency as well as the rejection capability against QCD-jets with the {\sc Atlas} detector are presented. The simulation, reconstruction and analysis are done in the framework of the {\sc Atlas} Data Challenge 1. This study includes the Level 1 Trigger, the Event Filter and the offline selection. It is based on fully simulated events at the initial low ($2\times 10^{33} {\rm cm^{-2}\ s^{-1}}$) and the design high ($10^{34} {\rm cm^{-2}\ s^{-1}}$) luminosity, on which pile-up is superimposed. For both luminosities, a jet rejection factor of $\sim 10^5$ can be obtained for an electron identification efficiency $\sim 78\%$.