Calibration and performance of the ATLAS Tile Calorimeter during the LHC Run 2

The Tile Calorimeter (TileCal) is the central section of the hadronic calorimeter of the ATLAS experiment and provides important information for reconstruction of hadrons, jets, hadronic decays of tau leptons and missing transverse energy. It also assists in muon identification. This sampling calorimeter uses steel plates as absorber and scintillating tiles as active medium. The light produced by the passage of charged particles through the latter is transmitted by wavelength shifting fibres to photomultiplier tubes (PMTs). The readout is segmented into about 5000 cells (longitudinally and transversally), each of them being read out by two PMTs in parallel. Among the TileCal calibration systems we mention a Cs radioactive source that illuminates the scintillating tiles, a laser light system to test the PMT response, and a charge injection system (CIS) for the front-end electronics. These, together with data collected during proton-proton collisions, provide extensive monitoring of the instrument and a means for equalizing the calorimeter cell response at each stage of the signal propagation. The performance of the TileCal has been established with cosmic ray muons and a large sample of proton-proton collisions. Response to high-momentum isolated muons is used to study the energy response, isolated hadrons are used as a probe for the hadronic response. The time resolution of the cells response is studied with multi-jet events. A description of the different TileCal calibration systems and results obtained during the LHC Run 2 are presented together with those from pile-up noise and response uniformity studies. The experimental results are compared with the simulated ones.