Test of the Standard Model of Electroweak Interactions by Measuring the Anomalous Tri-Linear Couplings.

A novel test of the gauge sector of the Standard Model (SM) of electroweak interactions--the first measurement of the tri-linear ZZgamma and Z gammagamma couplings--was carried out with the DO detector at the Fermilab Tevatron in {it p| p/} interactions at sqrt{s} = 1.8 TeV. We observed 4 (2) {it p| p/ }--> {it Z/}gamma + X events in the dielectron (dimuon) decay channel of the Z, with a total expected background of 0.5 +/- 0.1 events, which is in good agreement with SM predictions. The following limits on the anomalous CP-conserving and CP-violating h_sp{i0 }{V} couplings were obtained from fitting the p_sp{T}{gamma }^ectrum for a form factor scale of Lambda = 500 GeV (for the case when only one coupling is varied at a time): h_sp{10,30 }{Z} < 2.0, | h_sp{20,40}{Z}| < 0.5, | h_sp {10,30}{gamma}| < 2.1 , | h_sp{20,40} {gamma} < 0.5. The results are compared with recent data from the CDF and L3 experiments, as well as with the indirect limits from low energy measurements.