Study of Z boson pair production in e+e− collisions at LEP at s=189 GeV

The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e+e− collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74+0.15−0.14(stat.)±0.04(syst.)pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18+0.09−0.07(stat.)±0.02(syst.)pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.