Measurement of the top quark pair production cross section in the dilepton channel including a $\tau$ lepton in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

The cross section of the top quark pair production process $\mathrm{t\overline{t}}\rightarrow (\ell\nu_{\ell})(\tau_{\mathrm{h}}\nu_{\tau})\mathrm{b\overline{b}}$ is measured, where the $\tau_{\mathrm{h}}$ refers to the hadronic decays of the $\tau$ lepton, and $\ell=\mathrm{e},\mu$. The data sample corresponds to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$ and was collected in 2016 by the CMS detector in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$. The measured cross section is $\sigma_{\mathrm{t\overline{t}}} = 781 \pm 7\,\mathrm{(stat)} \pm 62\,\mathrm{(syst)} \pm 20\,\mathrm{(lumi)}\,\mathrm{pb}$. The ratio of the partial width $\Gamma(\mathrm{t}\rightarrow\tau\nu_{\tau}\mathrm{b})$ to the total width is measured to be $0.1050 \pm 0.0009\,\mathrm{(stat)} \pm 0.0071\,\mathrm{(syst)}$.