Study of neutral-current four-fermion and ZZ production in e+e− collisions at s= 183 GeV

A study of neutral-current four-fermion processes is performed using a data sample corresponding to 55.3 pb−1 of integrated luminosity collected by the L3 detector at LEP at an average centre-of-mass energy of 183 GeV. The neutral-current four-fermion cross sections for final states with a pair of charged leptons plus jets and with four charged leptons are measured to be consistent with the Standard Model predictions.Events with fermion pair masses close to the Z boson mass are selected in all observable final states and the ZZ production cross section is measured to be σZZ=0.30+0.22+0.07−0.16−0.03 pb, in agreement with the Standard Model expectation. No evidence for the existence of anomalous triple gauge boson ZZZ and ZZγ couplings is found and limits on these couplings are set.