Recent QCD results from ATLAS

The ATLAS collaboration has performed studies of a wide range of QCD phenomena. Recent soft-QCD measurements include studies of hadronic event shapes and double parton scattering. Differential measurements of inclusive-jet production provide stringent tests of higher order QCD predictions and provide input for determination of parton density functions. Jet-multiplicity ratios are sensitive to the strong coupling constant alpha_S and have reduced sensitivity to the uncertainties due to parton distribution functions. Measurements of the inclusive prompt isolated photon, photons in association with jets and diphoton cross sections provide a direct probe of short-distance physics, complementary to that from measurements of jets or vector-bosons, and are sensitive to the gluon density of the proton. The results are compared to next-to-leading-order or higher-order QCD calculations.