Abstract
A measurement is presented of the cross section for the electroweak production of a Z boson and a photon in association with two jets in proton–proton collisions at s=8 TeV. The Z bosons are identified through their decays to electron or muon pairs. The measurement is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb−1. The electroweak contribution has a significance of 3.0 standard deviations, and the measured fiducial cross section is 1.86−0.75+0.90(stat)−0.26+0.34(syst)±0.05(lumi) fb, while the summed electroweak and quantum chromodynamic total cross section in the same region is observed to be 5.94−1.35+1.53(stat)−0.37+0.43(syst)±0.13(lumi) fb. Both measurements are consistent with the leading-order standard model predictions. Limits on anomalous quartic gauge couplings are set based on the Zγ mass distribution.
Highlights
With the discovery of the Higgs boson at the CERN LHC [1, 2], the standard model (SM) became a great success
The high energy and luminosity of the LHC provides the opportunity to observe many processes that are predicted by the SM, including electroweak production of multiple gauge bosons (WVγ [3], Vγ γ [4,5,6]), vector boson scattering (VBS), and vector boson fusion (VBF) (EW W(Z)jj [13,14,15,16])
Same charge W±W± scattering has been observed by ATLAS, and the exclusive γ γ → W+W− process by CMS, both with significances larger than 3 standard deviations
Summary
With the discovery of the Higgs boson at the CERN LHC [1, 2], the standard model (SM) became a great success. Same charge W±W± scattering has been observed by ATLAS, and the exclusive γ γ → W+W− process by CMS, both with significances larger than 3 standard deviations. The triboson final state Zγ γ has been observed by ATLAS and CMS with a significance larger than 5 standard deviations. They are (a) bremsstrahlung, (b) multiperipheral (or nonresonant) production, (c, d) VBF with either two trilinear gauge boson couplings (TGC), or (e) VBS with quartic gauge boson couplings (QGC). Other backgrounds include jets or leptons misidentified as photons, diboson processes in which a W or Z boson decays into two jets and the photon originates from initial or final-state radiation, and contributions from top quark pairs and single top quark production
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