Measurement of differential top-quark-pair production cross sections in the lepton+jets channel with CMS

Normalised differential top-quark-pair (tt) production cross sections are measured in pp collisions at 7 and 8 TeV centre-of-mass energy with the CMS detector. Such distributions constitute a test of perturbative QCD at high energy scales and can help to constrain QCD parameters like parton distribution functions. Moreover, they can provide an improved description of tt background distributions for new physics searches and are sensitive to potential new physics effects themselves. The measurements are performed in the lepton+jets decay channels (e+jets and mu+jets) as a function of kinematic properties of the final-state charged leptons and b jets, as well as those of the top quarks and the tt system. The data are compared with several predictions from QCD calculations up to approximate next-to-next-to-leading-order precision. No significant deviations from the standard model are observed.