Calibration of the ATLAS Tile hadronic calorimeter using muons

The ATLAS Tile Calorimeter (TileCal) is the barrel hadronic calorimeter of the ATLAS experiment at the CERN Large Hadron Collider (LHC). It is a sampling calorimeter using plastic scintillator as the active material and iron as the absorber. TileCal , together with the electromagnetic calorimeter, provides precise measurements of hadrons, jets, taus and the missing transverse energy. Cosmic rays muons and muon events produced by scraping 450 GeV protons in one collimator of the LHC machine have been used to test the calibration of the calorimeter. The analysis of the cosmic rays data shows: a) the response of the third longitudinal layer of the Barrel differs from those of the first and second Barrel layers by about 3-4%, respectively and b) the differences between the energy scales of each layer obtained in this analysis and the value set at beam tests using electrons are found to range between -3% and +1%. In the case of the scraping beam data, the responses of all the layer pairs were found to be consistent within 1-2% uncertainties including systematic. They are compatible with one showing that the EM energy scale of TileCal in ATLAS is consistent with the value set using electrons at beam tests. The impact of the mentioned systematic uncertainties on the jet energy measurement in ATLAS was estimated to be 0.5%. A study using muons produced in p-p interactions is in progress.