Abstract
Several aspects of the jet production in pp collisions have been measured by the ATLAS collaboration using data collected at the LHC. The measurements of the production cross sections of inclusive, di- and three-jet events probe the dynamics of QCD and can constrain the parton proton structure. The cross sections are measured using jets clustered with the anti-kt algorithm with different distance parameters and compared to expectations based on next-to-leading order QCD calculations, corrected for non-perturbative and electroweak effects, as well as to next-to-leading order Monte Carlo simulations. Ratios of inclusive cross sections measured at different centre-of-mass energies allow for reduced experimental and/or theoretical uncertainties. Double-differential dijet and three-jet cross sections have been measured in proton-proton collisions at 7 TeV as a function of di- and three-jet masses and the jet rapidity separation. An NLO QCD analysis of the data indicates constraining power for parton distribution functions of the proton.
Highlights
The inclusive jet, dijet and three-jet cross sections are important tools for testing Quantum Chromodynamics (QCD) and searching for physics beyond the Standard Model at the LHC
The ATLAS Collaboration has published a first set of measurem√ents of the inclusive jet and dijet cross sections at s = 7 TeV, using an integrated luminosity of 17 nb−1 [2]
The measurement of the dijet [5] and of the inclusive jet [6] cross sec√tions using 4.7 fb−1 in the full 2011 data sample at s = 7 TeV show an improved precision comparing to the previous measurements
Summary
The inclusive jet, dijet and three-jet cross sections are important tools for testing Quantum Chromodynamics (QCD) and searching for physics beyond the Standard Model at the LHC. √ For the measurements based on the 2011 data at s = 7 TeV, a correction is applied to the energy of the topological clusters identified as hadronic by their topology and energy density It accounts for calorimeter response, dead material and out-of-cluster losses for pions, allowing to improve the energy resolution and to reduce the response dependence on the jet flavor. Additional energy due to pile-up interactions is subtracted by applying a correction depending on the number of reconstructed vertices in the event and the average number of collisions per bunch crossing This correction is derived in Monte Carlo simulation (MC) and validated in data, while the stability of the measurements under the pile-up conditions is checked. Because the potential correlations between the various uncertainty components are not perfectly known, two additional JES uncertainty configurations are considered, with stronger and weaker correlations comparing to the nominal one
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