Measurement of electroweak production of two jets in association with a Z boson in proton–proton collisions at $$\sqrt{s}=8\,\text {TeV}$$ s = 8 TeV

The purely electroweak (EW) cross section for the production of two jets in association with a Z boson, in proton–proton collisions at $$\sqrt{s}=8\,\text {TeV}$$ , is measured using data recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 19.7 $$\,\text {fb}^\text {-1}$$ . The electroweak cross section for the $$\ell \ell \mathrm {jj}$$ final state (with $$\ell = \mathrm {e}$$ or $$\mu $$ and j representing the quarks produced in the hard interaction) in the kinematic region defined by $$M_{\ell \ell } >50$$ $$\,\text {GeV}$$ , $$M_\mathrm {jj} >120$$ $$\,\text {GeV}$$ , transverse momentum $$p_\mathrm {T j}> 25$$ $$\,\text {GeV}$$ , and pseudorapidity $$|\eta _\mathrm {j} |< 5$$ , is found to be $$\sigma _\mathrm {EW}(\ell \ell \mathrm {jj})=174 \pm 15\,\text {(stat)}\pm 40\,\text {(syst)}\text {\,fb}$$ , in agreement with the standard model prediction. The associated jet activity of the selected events is studied, in particular in a signal-enriched region of phase space, and the measurements are found to be in agreement with QCD predictions.