Identification of high pT electrons by the Second Level Trigger of ATLAS

In the trigger, electron identification is performed within Regions of Interest (RoI) identified by the first level (LVL1) trigger. The second level (LVL2) trigger selection consists of three stages: firstly a selection of electromagnetic clusters using the full calorimeter granularity, secondly a track search in the inner detector (ID), and finally a decision based on cuts on the reconstructed track parameters. These cuts include requirements for the matching in position and ET/pT of the inner detector track with the calorimeter cluster. In this note, the first two stages are outlined briefly. A detailed description is given of the selection cuts used in the final stage. The selection power of the various cuts is shown in terms of efficiencies for single isolated electrons and trigger rates determined from samples of jet events. The overall performance is illustrated with examples of efficiency and trigger rate at low and design luminosities given for several cut combinations.