Electron Identification Studies for the Level 1 Trigger Upgrade

We show that it is not possible to reject neutral pions from electrons at Level 1 trigger of the ATLAS trigger system. The lateral profiles of electrons and neutral pions are different when the interaction point of the colliding protons is at $z=0$ and a good rejection criteria is achieved. Although this rejection criteria is stable against increasing pileup, it fails for a more realistic model of the luminous profile of the proton beam. A variable used at Level 2 trigger is also shown in this note to be unstable against increasing pileup.