Status of the ATLAS Pixel Detector at the LHC and its performance after three years of operation

The ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN, providing high-resolution measurements of charged particle tracks in the high radiation environment close to the collision region. This capability is very important for the identification and measurement of proper decay times of long-lived particles such as b-hadrons, and thus vital for the ATLAS physics program. The detector provides hermetic coverage with three cylindrical layers of pixel detectors and three layers end-caps on each side. It consists of approximately 80 × 10 6 pixels that are individually read out via chips bump-bonded to 1744 n-in-n silicon substrates. The detector performance is excellent: ∼ 96 % of the pixels are operational, noise occupancy and hit efficiency exceed the design specification, and a good alignment allows high quality track resolution.