Measurements of the pp to ZZ production cross section and the Z to 4l branching fraction, and constraints on anomalous triple gauge couplings at sqrt(s) = 13 TeVстатья
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Дата последнего поиска статьи во внешних источниках: 17 апреля 2018 г.
Аннотация:Four-lepton production in proton-proton collisions, pp→(Z/γ∗)(Z/γ∗)→4ℓ, where ℓ=e or μ, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb−1. The ZZ production cross section, σ(pp→ZZ)=17.2±0.5 (stat) ±0.7 (syst) ±0.4(theo)±0.4 (lum) pb, measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60<mℓ+ℓ−<120 GeV, is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be B(Z→4ℓ)=4.8±0.2 (stat) ±0.2 (syst) ±0.1 (theo) ±0.1 (lum) ×10−6 for events with a four-lepton invariant mass in the range 80 <m4ℓ< 100 GeV and a dilepton mass mℓℓ>4 GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings at 95% confidence level: −0.0012<fZ4<0.0010, −0.0010<fZ5<0.0013, −0.0012<fγ4<0.0013, −0.0012<fγ5<0.0013.