Inclusive and differential cross section measurements of $\mathrm{t}\mathrm{\overline{t}}\mathrm{b}\mathrm{\overline{b}}$ production in the lepton+jets channel at $\sqrt{s}=13\,\mathrm{TeV}$ with the CMS detector

Measurements of inclusive and differential cross sections of the associated production of top quark and $\mathrm{b}$ quark pairs, $\mathrm{t}\mathrm{\overline{t}}\mathrm{b}\mathrm{\overline{b}}$, are presented. The results are based on LHC data from proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $138\,\mathrm{fb}^{-1}$. The cross sections are measured in the lepton+jets decay channel of the top quark pair, using events containing exactly one isolated electron or muon and at least five jets. These cross sections are measured in four fiducial phase space regions, targeting different aspects of the $\mathrm{t}\mathrm{\overline{t}}\mathrm{b}\mathrm{\overline{b}}$ process. The jets arising from the b quark pair are probed using two complementary approaches, one relying on kinematic variables at the stable particle level and another based on a dedicated multivariate identification algorithm exploiting the simulated event history. Distributions are unfolded to the particle level through maximum likelihood fits, and compared with predictions from several event generators. The inclusive cross section measurements of the fiducial phase space regions are the most precise measurements of $\mathrm{t}\mathrm{\overline{t}}\mathrm{b}\mathrm{\overline{b}}$ production so far. With one exception, the inclusive cross sections predicted by the considered event generators are $10-50\%$ lower than the measured values in the different phase space regions. The differential cross sections show varying degrees of compatibility with the theoretical predictions, whereby no generator simultaneously describes all the measured distributions.