Measurement of the cross section ratio σ_tt‾bb‾/σ_tt‾jj in pp collisions at √s = 8 TeV

The first measurement of the cross section ratio σ_tt‾bb‾/σ_tt‾jj is presented using a data sample corresponding to an integrated luminosity of 19.6fb⁻¹ collected in pp collisions at √s = 8 TeV with the CMS detector at the LHC. Events with two leptons (e or 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 p_T of both 20 and 40 GeV/c. The measured ratio is 0.022 ±0.003 (stat) ±0.005 (syst) for p_T > 20 GeV/c. The absolute cross sections σ_tt‾bb‾ and σ_tt‾jj are also measured. The measured ratio for p_T > 40GeV/c is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.