Jet energy scale and its systematic uncertainty in proton-proton collisions at sqrt(s)=7 TeV with ATLAS 2011 data

The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of sqrt(s) = 7 TeV corresponding to an integrated luminosity of 4.7 fb−1. Jets are reconstructed from topological clusters of calorimeter cells using the anti-kt algorithm with distance parameters R = 0.4 or R = 0.6, and are calibrated using Monte Carlo simulation. A residual JES correction is applied to account for differences between data and Monte Carlo. This correction and its systematic uncertainty are evaluated in bins of jet pseudorapidity and transverse momenta, for jets with calibrated transverse momenta pjet > 20 GeV and pseudorapidities |eta| < 4.5. It is estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a Z boson for 20 ≤ pjet < 1000 GeV. The effect of multiple proton-proton interactions is corrected for and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1% is found in the central calorimeter region (|eta| < 1.2) for jets with 55 ≤ pjet < 500 GeV. For central jets at lower pT the uncertainty is about 3%. A consistent JES estimate is found using in situ single hadron response measurements and from test beam results, which provide the estimate for pjet > 1 TeV. The calibration of forward jets is derived from dijet pT balance measurements. The resulting uncertainty reaches its largest value of 6% for low-pT jets at |eta| = 4.5. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5-3%.