Measurement of the cross section ratio sigma(t t-bar b b-bar) / sigma(t t-bar jj) in pp collisions at sqrt(s) = 8 TeV

The CMS collaboration
Khachatryan, Vardan , Sirunyan, Albert M , Tumasyan, Armen , Adam, Wolfgang , Bergauer, Thomas , Dragicevic, Marko , Erö, Janos , Fabjan, Christian , Friedl, Markus , Fruehwirth, Rudolf
Phys.Lett.B 746 (2015) 132-153, 2015.

Abstract (data abstract)
CERN-LHC. The first measurement of the cross section ratio $t\bar{t}b\bar{b}$ / $t\bar{t}jj$ is presented using a data sample corresponding to an integrated luminosity of 19.6 inverse femtobarns collected in pp collisions at $\sqrt{s}$ = 8 TeV with the CMS detector at the LHC. Events with two leptons ($e$ or $\mu$) 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 pt of both 20 and 40 GeV. The measured ratio is 0.022 $\pm$ 0.003 (stat.) $\pm$ 0.005 (syst.) for $p_{\rm T}$ > 20 GeV. The absolute cross sections $t\bar{t}b\bar{b}$ and $t\bar{t}jj$ are also measured. The measured ratio for $p_{\rm T}$ > 40 GeV is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.

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