Probing the measurement of jet energies with the ATLAS detector using photon+jet events in proton-proton collisions at sqrt{s} = 7 TeV

The energy calibration of jets produced in proton-proton collisions at sqrt(s) = 7 TeV is probed in situ in the region |eta| < 1.2 of the ATLAS detector by exploiting the conservation of transverse momentum (pT) in events with a photon and a jet. The measurement is performed using the 2011 data set corresponding to an integrated luminosity of 4.7 fb-1, and covers the photon transverse momentum (pT(gamma)) range from 25 GeV to 800 GeV. Two methods are used to compare the calorimeter response to jets in data and Monte Carlo simulation: the direct transverse momentum balance (pT(jet)/pT(gamma)), and a technique where the photon transverse momentum is balanced against all the observed energy flow separate from the photon. The jet pT response in data is found to be ~2% smaller than that in the Monte Carlo simulation for pT(gamma) higher than 85 GeV. The total uncertainty on the in situ calibration techniques is smaller than 1% in the range 110 < pT(gamma) < 500 GeV.