Response and shower topology of 2 to 180 GeV pions measured with the ATLAS barrel calorimeter at the CERN test-beam and comparison to Monte Carlo simulations

The response of the ATLAS barrel calorimeterto pions with momenta from 2 to 180 GeV is studied in a test–beam at the CERN H8 beam line. The mean energy, the energy resolution and the longitudinal and radial showerprofiles, and, various observables characterising the showertopology in the calorimeterare measured. The data are compared to Monte Carlo simulations based on a detailed description of the experimental set–up and on various models describing the interaction of particles with matter based on Geant4.