Commissioning of the ATLAS electron, photon and tau trigger selection

Since March 2010, the ATLAS experiment has been recording proton-proton collisions of the Large Hadron Collider (LHC) at a center of mass energy of 7 TeV. At low instantaneous luminosity, data were selected by the hardware based Level-1 trigger and processed by the software based High Level Trigger (HLT) without active rejection; as the luminosity increased, the HLT rejection has been gradually activated. Since then, electrons from J/ψ, bottom, charm, W and Z decays, prompt photons and a first sample of tau hadronic decays from W have been efficiently selected. This paper gives an overview of the implementation of the electron, photon and tau trigger selection algorithms and of the first experience running these triggers online. The performance of the three trigger levels is discussed and a set of comparisons of the online discriminating variables with offline reconstruction is shown, as well as the comparison of data with the Monte Carlo simulation on which the current selection was tuned.