Abstract
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 ,,text{ fb }^{-1}. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-k_{t} algorithm with distance parameters R=0.4 or R=0.6, and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are 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} le p_{mathrm {T}}^mathrm {jet}<{1000}, ~mathrm{GeV } and pseudorapidities |eta |<{4.5}. 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} le p_{mathrm {T}}^mathrm {jet}<{500}, ~mathrm{GeV }. For central jets at lower p_{mathrm {T}}, the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton–proton collisions and test-beam data, which also provide the estimate for p_{mathrm {T}}^mathrm {jet}> 1 TeV. The calibration of forward jets is derived from dijet p_{mathrm {T}} balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-p_{mathrm {T}} 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 %.
Highlights
Jets are the dominant feature of high-energy, hard proton– proton interactions at the Large Hadron Collider (LHC) at CERN
The study in the sample without b-tagging covers up to approximately 2 TeV, and provides a cross check over almost the full range of calibrated pT studied in situ through the analyses used to establish the systematic uncertainty on the jet energy scale in ATLAS
Agreement of the Monte Carlo (MC) simulations with the data for the rtrk measurements is found within systematic uncertainties across all pT for inclusive jets and for pTjet < 400 GeV for b-tagged jets
Summary
Jets are the dominant feature of high-energy, hard proton– proton interactions at the Large Hadron Collider (LHC) at CERN. Jets are observed as groups of topologically related energy deposits in the ATLAS calorimeters, associated with tracks of charged particles as measured in the inner tracking detector They are reconstructed with the anti-kt jet algorithm [1] and are calibrated using Monte Carlo (MC) simulation. A reduced uncertainty of about 2.5 % in the central calorimeter region over a wide pT range of 60 pT < 800 GeV was achieved after applying the increased knowledge of the detector performance obtained during the analysis of this first year of ATLAS data taking [3] This estimation used single-hadron calorimeter response measurements, systematic variations of MC simulation configurations, and in situ techniques, where the jet transverse momentum is compared to the pT of a reference object. ATLAS anti-kt jets, R = 0.6 LCW+JES scheme, for both data and MC simulations, as a function of the photon transverse momentum. This is confirmed by studying the response variation after relaxing the photon identification criterion
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