A study of Z boson pair production in e(+)e(-) annihilation at center-of-mass energies near 183 GeV and 189 GeV is reported. Final states containing only leptons, (l(+)l(-)l(+)l(-) and l(+)l(-) v (v) over bar), quark and lepton pairs, (q (q) over bar l(+)l(-), q (q) over bar v (v) over bar) and the all-hadronic final state (q (q) over bar q (q) over bar) are considered. In all states with at least one Z boson decaying hadronically, q (q) over bar and b (b) over bar final states are considered separately using lifetime and event-shape tags, thereby improving the cross-section measurement. At root s = 189 GeV the Z-pair cross section was measured to be 0.80(-0.13)(+0.14)(stat.)(-0.05)(+0.06)(syst.) pb, consistent with the Standard Model prediction. At root s = 183 GeV the 95% C.L. upper limit is 0.55 pb. Limits on anomalous ZZ gamma and ZZZ couplings are derived. (C) 2000 Published by Elsevier Science B.V. All rights reserved.
