b-Tagging Algorithms and their Performance at ATLAS
  The ability to identify jets containing B hadrons is important for the high-pT physics program of a general-purpose experiment such as ATLAS. b-tagging is in particular useful for selecting very pure top quark samples, for studying standard model or supersymmetric Higgs bosons which couple preferably to heavy objects, for vetoing backgrounds for several physics channels and finally for searching for new physics beyond the standard model like supersymmetric particles or heavy gauge bosons. After a review of the algorithms used to identify b-jets, their anticipated performance is discussed as well as the impact of selected critical ingredients such as residual misalignments in the tracker. The prospects to measure the b-tagging performance in the first few hundreds pb-1 of data with di-jet events as well as ttbar events are presented. Finally three different physics use cases of b-tagging are summarised. 
Marc Lehmacher