Electroweak production of two jets in association with a Z boson in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A measurement of the electroweak (EW) production of two jets in association with a Z boson in proton-proton collisions at $\sqrt{s}=$ 13 TeV is presented, based on data recorded in 2016 by the CMS experiment at the LHC corresponding to an integrated luminosity of 35.9 fb${}^{-1}$. The measurement is performed in the $\mathrm{\ell }\mathrm{\ell }\mathrm{j}\mathrm{j}$ final state with $\mathrm{\ell }$ including electrons and muons, and the jets j corresponding to the quarks produced in the hard interaction. The measured cross section in a kinematic region defined by invariant masses $m_{\mathrm{\ell }\mathrm{\ell }}>$ 50 GeV, $m_{\mathrm{j}\mathrm{j}}>$ 120 GeV, and transverse momenta $p_{\mathrm{T}\mathrm{j}}>$ 25 GeV is ${\sigma }_{\mathrm{E}\mathrm{W}}(\mathrm{\ell }\mathrm{\ell }\mathrm{j}\mathrm{j})=$ 534 $\pm$ 20 (stat) $\pm$ 57 (syst) fb, in agreement with leading-order standard model predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. No evidence is found and limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are $-2.6 < c_{WWW}/\Lambda^2 < 2.6 $TeV$^{-2}$and$-8.4 < c_{W}/\Lambda^2 < 10.1 $TeV$^{-2}$. The additional jet activity of events in a signal-enriched region is also studied, and the measurements are in agreement with predictions.