Low pT-physics in ATLAS

The measurement of the properties of proton-proton interactions at center-of-mass energies 900 GeV and 7 TeV in the ATLAS detector are presented. The charged-particle density, its dependence on transverse momentum and pseudo-rapidity, and the relationship between transverse momentum and charged-particle multiplicity are measured for events in a defined kinematic range. Distributions sensitive to underlying event in proton-proton collisions are also discussed as well as angular azimuthal correlation of charged particles. The measurements are compared to Monte Carlo models for inelastic events.