Abstract
The production of Z boson pairs in proton-proton ( pp ) collisions, pp → (Z/γ∗)(Z/γ∗) → 2ℓ2ℓ' , where ℓ, ℓ' = e or μ , is studied at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 137 fb-1 , collected during 2016-2018. The ZZ production cross section, σtot(pp → ZZ) = 17.4 ± 0.3 (stat) ± 0.5 (syst) ± 0.4 (theo) ± 0.3 (lumi) pb , measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region 60 < mℓ+ℓ- < 120 GeV is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings.