Measurement of the cross section for $\mathrm{t}\bar{\mathrm{t}}$ production with additional jets and b jets in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

The cross sections of top quark pair production in association with a pair of jets from bottom quarks ($\sigma_{\mathrm{t}\bar{\mathrm{t}}\mathrm{b}\bar{\mathrm{b}}}$) and in association with a pair of jets from quarks with any flavor or gluons ($\sigma_{\mathrm{t}\bar{\mathrm{t}}\mathrm{jj}}$) and their ratio are measured in proton-proton collisions at a center-of-mass energy of $13~\mathrm{TeV}$ with data collected in 2016 by the CMS detector at the LHC, corresponding to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$. The measurements are performed in the visible phase space in the dilepton and lepton+jets channels separately, by fitting the distribution of the b tagging discriminant variable of the two jets that do not belong to the $\mathrm{t}\bar{\mathrm{t}}$ decay. The $\mathrm{t}\bar{\mathrm{t}}\mathrm{jj}$ cross sections in the visible phase space in the dilepton and the lepton+jets channel are measured to be 2.36 $\pm$ 0.02 (stat) $\pm$ 0.20 (syst) pb and 31.0 $\pm$ 0.2 (stat) $\pm$ 2.9 (syst) pb, respectively. The measured cross section ratio in the visible phase space is 0.017 $\pm$ 0.001 (stat) $\pm$ 0.001(syst) for the dilepton channel, and 0.020 $\pm$ 0.001 (stat) $\pm$ 0.001 (syst) for the lepton+jets channel. The results extrapolated to the full phase space are compared with the standard model expectations obtained at next-to-leading order.