Energy Flow Objects and Usage of Tracks for Energy Measurement in CMS

We present an algorithm to determine the energy of jets using the CMS calorimeter and tracker. The results on dijet mass reconstruction for a hypothetical Z'(M=120 GeV)->jj are presented. Improvement in Z'mass resolution when the energy flow objects are used is found to be about of 22 % in comparison with the usage of the calorimeter information only. We present also a method to improve jet energy resolution with regional use of tracks when a jet is found first with a ''standard'' jet finder running on calorimeter towers as an input. We factorize the improvement in the jet energy resolution due to addition of tracks swept out of the reconstruction cone in 4T magnetic field, and due to replacement inside cone of the cluster energy by the matched track momentum or (for bad matching) subtraction from the jet energy the expected response of the track in the calorimeter and adding to the jet energy the track momentum. It is shown that for the soft jets of ~ 30-40 GeV the energy resolution may be improved by factor 1.5.