First measurement of jets and missing transverse energy with the ATLAS calorimeter at √s = 900 GeV and √s = 7 TeV

In December 2009, ATLAS recorded the first proton-proton collisions delivered by the LHC at a center-of-mass energy of √s = 900 GeV, and at √s = 7 TeV beginning in March 2010. We report on the first measurements of the kinematic distributions of jets and missing transverse energy at both center-of-mass regimes. These data also provide the opportunity to test the inputs tojet reconstruction and thejet calibration schemes available in ATLAS. Basic jet properties such as the number of associated charged particles, the longitudinal and radial shower topology in jets, and the transverse energy profiles of jets are compared to Monte Carlo simulation of the full detector response. We show that the basic inputs tojet reconstruction and calibration are generally well modeled by these simulations and that discrepancies will help to guide future Monte Carlo tunings and detector response descriptions.