Measurement of Jets with the CMS Detector at the LHC

The jet reconstruction algorithms and calibration techniques implemented in the CMS reconstruction software are studied with high-statistics Monte Carlo samples of QCD dijet events. Generated events are passed through a full detector-level simulation of the CMS detector including readout digitization in the presence of pile-up at an instantaneous luminosity of L = 2× 10 cms. Effects of detector resolution and granularity on the jet resolutions, efficiencies and instrumental background rates are estimated. These measures of performance are compared for a set of jet algorithms, algorithm parameters, and calorimeter cell thresholds. The uniformity and linearity of the jet response are evaluated by comparing particle-level and reconstructed jets over a wide range of transverse momenta throughout the angular coverage of the calorimeters. Fits to the ratio of reconstructed to generated jet transverse energy give a transverse energy resolution of 10-15% (8-10%) at 100 GeV (200 GeV) over the pseudorapidity range 0 < |η| < 5. The angular resolution for 100 GeV (200 GeV) jets is 0.02-0.035 (0.02) radians. ∗) On leave from GSU, Gomel, Belarus