Measurement of the electroweak production of Z$\gamma$ and two jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV and constraints on anomalous quartic gauge couplings

Bethani, Agni [UCL] Bruno, Giacomo [UCL] Bury, Florian [UCL] Caputo, Claudio [UCL] David, Pieter [UCL] Delaere, Christophe [UCL] Donertas, Izzeddin Suat [UCL] Giammanco, Andrea [UCL] Jaffel, Khawla [UCL] Jain, Sandhya [UCL] Lemaitre, Vincent [UCL] Mondal, Kuntal [UCL] Prisciandaro, Jessica [UCL] Taliercio, Angela [UCL] Teklishyn, Maksym [UCL] Tran, Tu Thong [UCL] Vischia, Pietro [UCL] Wertz, Sébastien [UCL] et al.

The first observation of the electroweak (EW) production of a Z boson, a photon, and two forward jets (Z$\gamma$jj) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. A data set corresponding to an integrated luminosity of 137 fb$^{-1}$, collected by the CMS experiment at the LHC in 2016-2018 is used. The measured fiducial cross section for EW Z$\gamma$jj is $\sigma_{\mathrm{EW}}$ = 5.21 $\pm$ 0.52 (stat) $\pm$ 0.56 (syst) fb = 5.21 $\pm$ 0.76 fb. Single-differential cross sections in photon, leading lepton, and leading jet transverse momenta, and double-differential cross sections in $m_{\mathrm{jj}}$ and $\lvert\Delta\eta_{\mathrm{jj}}\rvert$ are also measured. Exclusion limits on anomalous quartic gauge couplings are derived at 95% confidence level in terms of the effective field theory operators $\mathrm{M}_{0}$ to $\mathrm{M}_{5}$, $\mathrm{M}_{7}$, $\mathrm{T}_{0}$ to $\mathrm{T}_{2}$, and $\mathrm{T}_{5}$ to $\mathrm{T}_{9}$.