Hard QCD Measurements in ATLAS

Proton-Proton collisions at the LHC offer the possibility to study perturbative QCD at unprecedented small distances. Various observables involving jets enable detailed tests of up to date MC generators as well as NLO calculations in a new region of phase space opened by the large centreof- mass energy provided by the LHC. The extension of the kinematic reach w.r.t. the Tevatron for inclusive jet and multijet transverse momentum spectra and for dijet mass spectra was possible already in the initial phase of data taking with a relatively small amount of integrated luminosity due to the large QCD cross section in proton–proton interaction with a centre–of–mass energy of ps = 7TeV. Here we review QCD measurements involving jets from the initial data taking phase of LHC which are well described in the framework of pertubative QCD. An alternative approach to jet observables offers the study of prompt photon production which is also being investigated with first data. In additon to proton–proton interactions, jets have also been studied in the first run of heavy ion collisions where a significant dijet asymmetry has been observed.