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 slates 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 a
ll observable final states and the ZZ production cross section is measured
to be sigma ZZ = 0.30(-0.16-0.03)(+0.22 + 0.07) pb, in agreement with the S
tandard Model expectation. No evidence for the existence of anomalous tripl
e gauge boson ZZZ and ZZ gamma couplings is found and limits on these coupl
ings are set. (C) 1999 Elsevier Science B.V. All rights reserved.