Charged particle multiplicities in proton-proton collisions at 900 GeV and 7 TeV center of mass energies

The measurement of the charged particle multiplicities with the ATLAS detector in inelastic $p-p$ collisions at center of mass energies 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 is measured for events with at least two charged particles in the kinematic range $|\eta| < 2.5$ and $p_T > 100$ MeV. The measurements are compared to different Monte Carlo model predictions.