Charged particle multiplicity and correlations in heavy ion collisions in the ATLAS experiment

Since the start of LHC the ATLAS experiment has collected data from pp, PbPb and recently pPb collisions. In this talk two topics from the heavy ion programme are presented. The first of them is the multiplicity of charged particles in PbPb collisions studied as a function centrality. In such collisions very high pseudorapidity particle density is obtained, reaching 1738 $pm$ 76 at $eta sim 0$. For the pPb collisions the latest analysis of two-particle correlations is presented. The "ridge" observed in pp events with large multiplicities is present also in central pPb collisions selected by large $Sigma E_{T}$ at the Pb fragmentation side. In the azimuthal correlation for $2 < Deltaeta < 5$ two components can be extracted. Assuming that in the peripheral collisions only the correlation due to momentum conservation effects are present, in the central collisions additional quadruple modulation component can be identified