Measurement of the electroweak production of Z$\gamma$ and two jets in proton-proton collisions at $\sqrt{s} = 13$ TeV and constraints on dimension 8 operators

A measurement of the electroweak (EW) production of a Z boson, a photon, and two jets (Z$\gamma$jj) in proton-proton collisions and constraints on anomalous quartic gauge couplings are presented. Proton-proton collision data corresponding to an integrated luminosity of 137 fb$^{-1}$, collected with the CMS detector at the LHC, at a center of mass collision energy of $\sqrt{s}=$ 13 TeV are used. The signal is extracted by requiring a large dijet invariant mass ($m_{jj}$) and a large pseudorapidity separation between the two jets ($|\Delta\eta_{jj}|$). The fiducial cross section measured for the EW production is $\sigma_{EW} = 5.21 \pm 0.76$ fb $= 5.21 \pm 0.52 \textrm{ (stat)} \pm 0.56 \textrm{ (syst)}$ fb. The observed and expected signal significance is higher than 5 standard deviations. Differential cross sections as functions of the photon, leptons and jets leading transverse momenta distributions and the $m_{jj}$-$|\Delta\eta_{jj}|$ two-dimensional distribution are measured. Exclusion limits on the dimension-eight operators $M_{0-7}$ and $T_{0-2,5-9}$ in the effective field theory framework at $95\%$ confidence level are reported.