Tagging b jets with electrons and muons at CMS

The first results of identification of jets from b quarks with soft-lepton tagging algorithms are presented in this note. Jets are built from the energy deposits in the electromagnetic and hadron calorimeters, with an iterative cone algorithm. Electrons and muons are searched for among the reconstructed charged particle tracks associated to these jets with an angular distance criterion. The muon identification is based on standard muon reconstruction algorithms, exploiting the dedicated muon detectors, while electron identification is based on the extrapolation of charged particle tracks into the calorimeter and a detailed analysis of the calorimeter clusters in the region around the track. Jets from b quarks are identified from the kinematic properties of the leptons relative to the jet and the significance of the three dimensional impact parameter of the lepton with respect to the event vertex. The effect of not incorporating the impact parameter significance, as would be necessary for data collected prior to the installation of the silicon pixel tracking detector, is also studied.