Underlying event studies and charged particle multiplicities in inelastic pp events with the ATLAS detector

Underlying event studies and charged particle multiplicities with the ATLAS detector in inelastic p–p collisions at center of mass energy of 900 GeV and 7 TeV are presented. The charged particle density, its dependence on pseudo-rapidity and transverse momentum and its correlation with the average transverse momentum are measured for events with at least two charged particles in the kinematic range image and image. For Underlying Event studies, the transverse momentum of charged tracks is required to be greater than 500 MeV. The measurements are compared with different Monte Carlo model predictions.