Commissioning of the ATLAS Tile Hadronic Calorimeter with Single Beam and First Collisions

TileCal, the central hadronic calorimeter of the ATLAS experiment at the CERN Large Hadron Collider (LHC), is built of steel and scintillating tiles with a double readout by optical fibers and uses photomultipliers as photodetectors. It provides measurements for hadrons, jets and missing transverse energy. In recent years TileCal has gone through an intensive commissioning phase. During this period several repairs of the front-end electronic components and low voltage power supplies were made, and all detector channels were fully tested using the dedicated calibration systems: cesium, laser and charge injection. Furthermore, cosmic muons and single beam data were used to verify the performance of the detector and check its readiness for the first collisions in 2009. The work to be presented will focus on the main results of the TileCal pre-collision commissioning phase and on the first results obtained with proton-proton collisions. The first proton-proton collisions at 900 GeV and 2360 GeV took place in the fall of 2009 and were used by TileCal for commissioning and performance studies. Measurements of energy response as a function of both eta and phi showed a good agreement between Monte Carlo and data. The analysis of the data from 2010 collisions allowed a deeper understanding of the TileCal performance.