Measurement of Jet Multiplicity Distributions in Top Quark Events With Two Leptons in the Final State at a centre-of-mass energy of 7 TeV

Jet multiplicity distributions are measured in pp collisions at $\sqrt{s} = 7$ TeV with the CMS detector using a dataset recorded in 2011 corresponding to an integrated luminosity of 5.0 fb$^{-1}$. The measurement is performed in the dileptonic decay channels ($\mu\mu$, ee and $\mu$e) of the top-antitop quark pairs, with at least two isolated leptons and at least one $b$-jet in the final state. The differential top anti-top quark cross section is measured as a function of the jet multiplicity. Furthermore, the distribution of the fraction of events without additional jets above a threshold is measured as functions of the jet transverse momentum and of the scalar sum of the transverse momenta of all additional jets. Several QCD calculations are compared with the data.