Measurement of the ZZ production cross section in the llvv channel in proton-proton collisions at sqrt(s)=7 TeV with the ATLAS detector

A measurement of the ZZ production cross section in proton-proton collisions at sqrt(s) = 7 TeV using data collected by the ATLAS experiment at the Large Hadron Collider is presented. In a data sample corresponding to an integrated luminosity of 4.7 fb−1 , 78 candidate events are observed in the channel with one Z boson decaying to a pair of electrons or muons and the second one decaying to a pair of neutrinos. After subtracting the expected background contribution, the signal amounts to 37.3 ± 4.3(stat.) ± 3.7(syst.) events. The total cross section for on-shell ZZ production has been determined to be σtot_ZZ = 5.4+1.3-1.2(stat.)+1.4-1.0(syst.) ± 0.2(lumi.) pb and is in agreement with the Standard Model expectation of 6.5+0.3 pb calculated at the next-to-leading order in QCD.