Measurement of the cross section ratio σ ttbb/σ ttjj in pp collisions at √s=8TeV

Abstract

The first measurement of the cross section ratio sttbb/sttjj is presented using a data sample corresponding to an integrated luminosity of 19.6fb-1 collected in pp collisions at vs=8TeV with the CMS detector at the LHC. Events with two leptons (eor µ) and four reconstructed jets, including two identified as b quark jets, in the final state are selected. The ratio is determined for a minimum jet transverse momentum pTof both 20 and 40GeV/c. The measured ratio is 0.022 ±0.003 (stat) ±0.005 (syst) for pT>20GeV/c. The absolute cross sections sttbb and sttjj are also measured. The measured ratio for pT>40GeV/c is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.