Abstract
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 $\mathrm{T}_{9}$.
Highlights
Vector boson scattering (VBS) processes are purely electroweak (EW) interactions at leading order (LO)
We present the first observation of EW Zγjj production
Other small contributions feature kinematic distributions similar to that of the dominant background and are estimated from simulation including single top quark events in the s- and t-channels that are normalized to their respective NLO cross sections; associated single top quark and W boson production normalized to its next-tonext-to-leading order (NNLO) cross section [39]; WW production normalized to its NNLO cross section; WZ, ZZ, QCD-induced Wγjj, and ttγ production normalized to their NLO cross sections
Summary
Vector boson scattering (VBS) processes are purely electroweak (EW) interactions at leading order (LO). Standard model (SM) EW production of Zγjj, which can proceed through VBS, can be extracted by exploiting the unique features of the VBS signature. We present the first observation of EW Zγjj production. Events corresponding to the lþl−γjj final states where l 1⁄4 e or μ, are selected, and the dijet system is required to satisfy the typical VBS signature. Previous experimental results for EW Zγjj production have been reported by the ATLAS [8] and CMS [9].
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