Jet energy measurement with the ATLAS detector in proton-proton collisions at $\sqrt{\mathrm{s}}=7\ \mathrm{TeV}$

Abstract

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √ s = 7 TeV corresponding to an integrated luminosity of 38 pb -1 .Jets are reconstructed with the anti-k t algorithm with distance parameters R = 0.4 or R = 0.6.Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta p T ≥ 20 GeV and pseudorapidities |η| < 4.5.The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations.The jet energy uncertainty is less than 2.5 % in the central calorimeter region (|η| < 0.8) for jets with 60 ≤ p T < 800 GeV, and is maximally 14 % for p T < 30 GeV in the most forward region 3.2 ≤ |η| < 4.5.The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon p T , the sum of the transverse momenta of tracks associated to the jet, or a system of low-p T jets recoiling against a high-p T jet.More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response.The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range.The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-p T jets.Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating ?e-mail: atlas.publications