The ATLAS Tile Calorimeter performance at LHC in pp collisions at 7 TeV

The Tile Calorimeter (TileCal), the central section of the hadronic calorimeter of the ATLAS experiment, is a key detector component to detect hadrons, jets and taus and to measure the missing transverse energy. Due to the very good muon signal to noise ratio it assists the muon spectrometer in the identification and reconstruction of muons. TileCal is built of steel and scintillating tiles coupled to optical fibers and read out by photomultipliers. The calorimeter is equipped with systems that allow to monitor and to calibrate each stage of the read-out system exploiting different signal sources: laser light, charge injection and a radioactive source. It also uses the minimus bias current integrated over thousands of LHC collisions to monitor the response stability and the LHC luminosity. The performance of the calorimeter has been measured and monitored using calibration data, random triggered data, cosmic muons, splash events and more importantly LHC collision events. The results presented assess the absolute energy scale calibration precision, the energy and timing uniformity and the synchronization precision. The results demonstrate a very good understanding of the performance of the Tile Calorimeter that is well within the design expectations.