Differential measurement of top-quark-pair production with additional jet activity \newline in the dilepton channel at CMS

Differential measurement of associated ttbar production with additional jets, including b jets, is presented. The measurement is performed in the dilepton decay channels (ee, mumu, emu) using data corresponding to an integrated luminosity of 19.6 fb-1 collected in pp collisions at centre-of-mass energy of 8 TeV with the CMS detector at the LHC.The absolute and normalised differential cross sections for ttbar production are measured as a function of the jet multiplicity for different jet-transverse-momentum thresholds, and as a function of kinematic properties of the leading additional jets. The differential ttbb cross sections are presented for the first time as a function of kinematic properties of the leading additional b jets. Furthermore, the fraction of events without additional jets above a transverse-momentum threshold is measured. The data are found to be consistent with predictions from several perturbative-QCD event generators and a next-to-leading order calculation.