Measurement of the cross section ratio σ[subscript t[bar over t]b[bar over b]]/σ[subscript t[bar over t]jj] in pp collisions at √s = 8 TeV

Abstract

The first measurement of the cross section ratio σ[subscript t[bar over t]b[bar over b]/σ[subscript t[bar over t]jj] is presented using a data sample corresponding to an integrated luminosity of 19.6 fb[superscript −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[subscript T] of both 20 and 40 GeV/c . The measured ratio is 0.022 ± 0.003(stat) ± 0.005(syst) for p[subscript T]>20 GeV/c. The absolute cross sections σ[subscript t[bar over t]b[bar over b] and σ[subscript t[bar over t]jj] are also measured. The measured ratio for p[subscript T]>40 GeV/c is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.