Latest QCD results in p+p and Pb+Pb collisions from ATLAS

The ATLAS experiment is measuring both p+p and Pb+Pb collisions at the largest energies available in laboratory delivered by the LHC accelerator. Tests of the Standard Model and searches for exotic phenomena require precise information on QCD processes, which are responsible for the background present in p+p interactions. In the heavy ion collisions the QCD processes are determining the properties of the Quark-Gluon Plasma which is created in the conditions of the extreme energy density. In this talk selected recent p+p results from the ATLAS experiment will be presented, including studies of jet properties and correlations in the multi-particle production. The effects of strong interactions in the dense matter created in Pb+Pb collisions observed as the jet suppression and the collective flow will be discussed in more detail. Slides of the talk to be given at the Excited QCD workshop in Peniche, Portugal, 6-12 May 2012