Response of single isolated hadrons in the ATLAS calorimeter

The response of the ATLAS calorimeter to single isolated hadrons has been measured in soft proton-proton collisions at a center-of-mass energy of 900 GeV. Isolated tracks with a momentum ranging between 0.5 to 10 GeV are selected in the pseudo-rapidity region up to 2.3. The energy deposit corresponding to each hadron is evaluated summing up all the clusters lying in appropriate calorimetric regions. The energy deposited in the calorimeter is compared to the track momentum. Data are compared to Monte Carlo simulation based on the Geant4 tool-kit. The response to hadrons at low momenta is described by the Monte Carlo simulation with an accuracy of a few percent. Such measurements can be used to constrain the jet energy scale for early LHC data.