Measurement of the ZZ production cross section in $\ell\ell\ell'\ell'$ decays in pp collisions at $\sqrt{s} = 13$ TeV

The ZZ production cross section is measured in proton-proton collisions at center-of-mass energy 13 TeV with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 1.3 fb$^{-1}$ is used. The cross section $\sigma(\mathrm{pp} \to \mathrm{ZZ})$ is inferred from measurements performed in the leptonic decay modes $\mathrm{ZZ} \to \ell\ell\ell'\ell'$, where $\ell, \ell' = \mathrm{e}, \mu$. The measured cross section, $\sigma(\mathrm{pp} \to \mathrm{ZZ}) = 16.7 ^{+2.9}_{-2.6} \mathrm{(stat)} ^{+0.7}_{-0.5} \mathrm{(syst)} \pm 0.3 \mathrm{(theo)} \pm 0.8 \mathrm{(lum)}~\text{pb}$, for both Z bosons produced in the mass region $60 < m_{\rm{Z}} < 120~\rm{GeV}$, is consistent with standard model predictions.