Measurement of the ZZ production cross section and Z →ℓ+ℓ−ℓ′+ℓ′− branching fraction in pp collisions at s√=13 TeV

Abstract

Four-lepton production in proton-proton collisions, pp -> (Z/gamma*)(Z/gamma*)-> l(+)l(-)l '(+)l '(-), where l,l '(-) = 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 2.6fb(-1). The ZZ production cross section, sigma(pp -> ZZ) = 14.6(-1.8)(+1.9)(stat)(-0.3)(+0.5) (syst) +/-0.2 (theo) +/-0.4 (lumi) pb, is measured for events with two opposite-sign, sameflavor lepton pairs produced in the mass region 60 < m(l+l-) m (l'+l'-) < 120GeV. The Z boson branching fraction to four leptons is measured to be B(Z -> l(+)l(-)l '(+)l '(-)) = 4.9(-0.7)(+0.8)(stat)(-0.2)(+0.3)(syst)(-0.1)(+0.2)(theo) +/- 0.1 (lumi) x10(-6) for the four-lepton invariant mass in the range 80 < m(l+)l-l'+l' < 100GeVand dilepton mass m(l+l-) > 4GeVfor all opposite-sign, same-flavor lepton pairs. The results are in agreement with standard model predictions.