Measurement of the cross section for electroweak production of $Zγ$ in association with two jets and constraints on anomalous quartic gauge couplings in proton–proton collisions at $\sqrt{s} = 8$ TeV

Abstract

A measurement is presented of the cross section for the electroweak production of a Z boson and a photon in association with two jets in proton–proton collisions at $\sqrt{s} = 8$ TeV. The Z bosons are identified through their decays to electron or muon pairs. The measurement is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 $fb^{−1}$. The electroweak contribution has a significance of 3.0 standard deviations, and the measured fiducial cross section is $1.86^{+0.90}_{−0.75}(stat)^{+0.34}_{−0.26}(syst)±0.05(lumi)$ fb, while the summed electroweak and quantum chromodynamic total cross section in the same region is observed to be $5.94^{+1.53}_{−1.35}(stat)^{+0.43}_{−0.37}(syst)±0.13(lumi)$ fb. Both measurements are consistent with the leading-order standard model predictions. Limits on anomalous quartic gauge couplings are set based on the $Zγ$ mass distribution.