"Commissioning and Performance of the ATLAS muon, electron, tau and Bphysics triggers with 7 TeV collisions at the LHC"

In order to cope with the large rate of proton collisions at the LHC, the ATLAS experiment is equipped with a complex three level trigger system, where the first level (L1) is entirely implemented in custom built hardware and the two successive levels (referred together as High Level Triggers - HLT) are software selection algorithms running on large PC farms. Since March 30, 2010, the LHC has been successfully providing 7 TeV proton-proton collisions, resulting in a total integrated luminosity of a few hundred inverse nanobarns. These data have been very useful to assess the performance of the ATLAS detector and trigger. In particular, the ATLAS muon, electron, tau and Bphysics triggers have been validated and trigger strategies have been developed to manage increasing luminosity. These triggers are very important for example for new physics discoveries at the LHC, as they allow efficient collection of the signal events while keeping the background rate within the allowed bandwidth. During 2010 they have been commissioned in various stages. Firstly, the rejection was applied only at L1 and the HLT was run online in pass-through mode. This allowed a detailed study and optimization of the HLT algorithms without interfering with the data taking. With increasing luminosity the HLT has been activated to efficiently select leptons from J/Psi, bottom, charm, W and Z decays. This contribution focuses on the assessment of the relevant q uantities in the muon, electron, tau and Bphysics trigger selection, emphasizing the components which are fundamental in the decision making. The different strategies for trigger efficiency measurements will be presented. In addition, the evolution of the trigger menu, which will be vital in future physics measurements, will be described.