Measurement of electroweak production of Z gamma in association with two jets in proton-proton collisions at sqrt(s) = 13 TeV

A measurement of electroweak production of a Z boson and a photon in association with two jets in proton-proton collisions is presented. The Z boson candidates are selected through their decay into a pair of electrons or muons. The electroweak production of the Z$\gamma$jj final state is isolated by selecting events with a large dijet mass and a large rapidity gap between the two jets. The measurement is based on data collected with the CMS detector in $2016$ at a center-of-mass energy of $13$ TeV corresponding to an integrated luminosity of 35.9 $\text{fb}^{\text{-1}}$. The observed significance of the signal is $3.9$ standard deviations, where a significance of $5.2$ standard deviations is expected based on the standard model. The results are combined with previously published CMS results based on $\sqrt{s}=8$ TeV data, which leads to an observed (expected) significance of $4.7$ ($5.5$) standard deviations. A cross section measurement in a fiducial region is reported. Bounds are given on quartic vector boson interactions in the framework of dimension-8 effective field theory operators.