Search for new physics in the dijet mass distribution using 1 fb-1 of pp collision data at √s = 7 TeV collected by the ATLAS detector

Invariant mass distributions of jet pairs (dijets) produced in LHC proton-proton collisions at a centre-of-mass energy √s=7 TeV have been studied using a data set corresponding to an integrated luminosity of 1.0 fb-1 recorded in 2011 by ATLAS. Dijet masses up to ∼4 TeV are observed in the data, and no evidence of resonance production over background is found. Limits are set at 95% C.L. for several new physics hypotheses: excited quarks are excluded for masses below 299 TeV, axigluons are excluded for masses below 3.32 TeV, and colour octet scalar resonances are excluded for masses below 1.92 TeV

Study of jet shapes in inclusive jet production in pp collisions at √s = 7 TeV using the ATLAS detector

Jet shapes have been measured in inclusive jet production in proton-proton collisions at √s = 7  TeV using 3  pb-1 of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-kt algorithm with transverse momentum 30  GeV<pT<600  GeV and rapidity in the region |y|<2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and nonperturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described