b-Jet Tagging Performance in ATLAS

The efficient identification of jets originating from the fragmentation of b quarks is an essential ingredient in many physics topics addressed by the ATLAS experiment. The very good performance of the ATLAS detector in particular makes it possible to exploit a variety of lifetime tagging techniques, ranging from simple impact parameter and secondary vertexing algorithms to sophisticated decay chain reconstructions and versatile multivariate techniques combining individual inputs. A brief performance overview will be provided. The wealth of data collected by the experiment in Run 1 allows for precise calibrations of the performance of the tagging algorithms. In particular, the high b-jet purity that can be obtained in top quark pair candidate samples allows for novel and precise calibrations of the b-jet tagging efficiencies. These calibrations are combined with more traditional techniques to improve the precision further. Dedicated calibrations exist for the charm-jet and light-flavour jet tagging efficiencies. The ATLAS calibration status will be described in detail.