Measurement of the $ZZ$ production cross section and $Z \to \ell^+ \ell^- \ell^{\prime +} \ell^{\prime -}$ branching fraction in $pp$ collisions at $\sqrt{s} = 13$ TeV

Abstract

Four-lepton production in proton-proton collisions, $pp \to (Z/\gamma*)(Z/\gamma*) \to Z \to \ell^+ \ell^- \ell^{\prime +} \ell^{\prime -}$, where $\ell,\ell^\prime$ = e or $\mu$, 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 2.6 inverse femtobarns. The ZZ production cross section, $\sigma(pp \to ZZ) = 14.6^{+1.9}_{-1.8}$ (stat)$^{+0.5}_{-0.3}$(syst)$\pm$ 0.2 (theo) $\pm$ 0.4 (lumi) pb, is measured for events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 $$ 4 GeV for all opposite-sign lepton pairs. The results are in agreement with standard model predictions