Measurement of the Luminosity by the ATLAS Experiment

The luminosity is a fundamental parameter of a particle collider. The success of physics programme of ATLAS experiment depends on the precise determination of the luminosity. Several detectors have been used during the 2010-2011 data taking for the measurement of the luminosity and for monitoring its evolution as a function of time. The absolute calibration is performed using dedicated beam-separation scans which allows the determination of the luminosity without prior knowledge of the detector efficiency and inelastic pp cross section. Based on this method ATLAS has determined the luminosity with an uncertainty of 3.7%. A summary of the luminosity calibration methods and results are presented in this poster.