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

The collaboration
Phys.Rev.D 104 (2021) 072001, 2021.

Abstract (data 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 $\sigma_{\mathrm{EW}}=5.21\pm0.52\,\mathrm{stat}\,\pm0.56\,\mathrm{syst}\,\mathrm{fb}=5.21\pm0.76\mathrm{fb}$. Single-differential cross sections in photon, leading lepton, and leading jet transverse momenta, and double-differential cross sections in $m_{\mathrm{jj}}$ and $|\Delta\eta_{\mathrm{jj}}|$ 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 $\mathrm{T}_{9}$. The fiducial region is defined as (selection is in the generator-level): - $p_{\mathrm{T}}^{l}>$ 20 GeV (25 GeV) && $|\eta^{l}|<$ 2.4 (2.5) for muon(electron) - 70 $<m_{ll}<$ 110 GeV - $p_{\mathrm{T}}^{\gamma}>$ 20 GeV && $|\eta^{\gamma}|<$ 1.4442 or ($|\eta^{\gamma}>|$ 1.566 && $|\eta^{\gamma}|<$ 2.5) - $p_{\mathrm{T}}^{j}>$ 30 GeV && $|\eta^{j}|<$ 4.7 - $m_{jj}>$ 500 GeV && $|\Delta\eta_{jj}|>$ 2.5 - $\Delta R(l,\gamma)>$0.7 && $\Delta R(l,j)>$ 0.5 && $\Delta R(\gamma,j)>$ 0.5 && $\Delta R(j,j)>$ 0.5 - leptons are dressed with photons whose $\Delta R(l,\gamma)<$ 0.1 Selection for aQGC limits are defined as (selection is in the reconstruction-level): - $p_{\mathrm{T}}^{l}>20$ GeV (25 GeV) && $|\eta^{l}|<$ 2.4 (2.5) for muon(electron) - 70 $<m_{ll}<$ 110 GeV - $p_{\mathrm{T}}^{\gamma}>$ 120 GeV && $|\eta^{\gamma}|<$ 1.4442 or ($|\eta^{\gamma}|>$ 1.566 && $|\eta^{\gamma}|<$ 2.5) - $p_{\mathrm{T}}^{j}>$ 30 GeV && $|\eta^{j}|<$ 4.7 - $m_{jj}>$ 500 GeV && $|\Delta\eta_{jj}|>$ 2.5 - $\Delta R(l,\gamma)>$0.7 && $\Delta R(l,j)>$ 0.5 && $\Delta R(\gamma,j)>$ 0.5 && $\Delta R(j,j)>$ 0.5