Overview of the high-level trigger electron and photon selection for the ATLAS experiment at the LHC

The ATLAS experiment at the Large Hadron Collider (LHC) will face the challenge of efficiently selecting interesting candidate events in pp collisions at 14 TeV center-of-mass energy, whilst rejecting the enormous number of background events. The high-level trigger (HLT = second level trigger and event filter), which is a software based trigger will need to reduce the level-1 output rate of ap 75 kHz to ap 200 Hz written out to mass storage. In this talk, an overview of the current physics and system performance of the HLT selection for electrons and photons is given. The performance has been evaluated using Monte Carlo simulations and has been partly demonstrated in the ATLAS testbeam in 2004. The efficiency for the signal channels, the rate expected for the selection, the global data preparation and execution times were highlighted. Furthermore, some physics examples were discussed to demonstrate that the triggers are well adapted for the physics programme envisaged at the LHC