Abstract
Measurements of the mathrm{Z}mathrm{Z} production cross sections in proton–proton collisions at center-of-mass energies of 7 and 8~mathrm{TeV} are presented. Candidate events for the leptonic decay mode mathrm{Z}mathrm{Z}rightarrow 2mathrm{l} 2nu , where mathrm{l} denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6),text {fb}^text {-1} at 7 (8)~mathrm{TeV} collected with the CMS experiment. The measured cross sections, sigma (mathrm {p}mathrm {p}rightarrow mathrm{Z}mathrm{Z}) = 5.1_{-1.4}^{+1.5},text {(stat)} ,_{-1.1}^{+1.4},text {(syst)} pm 0.1,text {(lumi)} text {~pb} at 7~mathrm{TeV}, and 7.2_{-0.8}^{+0.8},text {(stat)} ,_{-1.5}^{+1.9},text {(syst)} ,pm , 0.2,text {(lumi)} text {~pb} at 8~mathrm{TeV}, are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the mathrm{Z}mathrm{Z} final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for mathrm{Z}mathrm{Z} in 4mathrm{l} final states, yielding the most stringent constraints on the anomalous couplings.
Highlights
The production of pairs of Z bosons in proton–proton collisions is a rare diboson process in the Standard Model (SM)
We expect that an accurate description of the ETmiss distribution and other related kinematic variables can be obtained from this photon + jets sample
Some corrections must be applied to the photon + jets sample to ensure a good modeling of the DY process
Summary
The production of pairs of Z bosons in proton–proton collisions is a rare diboson process in the Standard Model (SM). This paper presents measurements of the ZZ production cross sections in proton–proton collisions at the LHC at two different center-of-mass energies, 7 and 8 TeV, in the decay channel with two charged leptons, electrons (ee) or muons (μμ), and a neutrino-antineutrino pair of any flavor (νν). The production of ZZ pairs has been studied at the LHC by the ATLAS experiment, which analyzed the decay modes 2l2l and 2l2ν (l, l = e, μ) at 7 TeV [9], and by the CMS experiment, which considered 2l2l final states (l = e, μ and l = e, μ, τ ) at 7 TeV [10] and 8 TeV [11] Both experiments measured ZZ production cross sections in good agreement with the SM predictions and set limits on anomalous triple gauge couplings (ATGCs). Limits are computed and combined with existing results from CMS in the four-charged-lepton final state
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