The e+e-→Zγγ→q(q)over-barγγ reaction at LEP and constraints on anomalous quartic gauge boson couplings

The cross section of the process e(+)e(-) --> Zgammagamma --> q (q) over bar gammagamma is measured with 215 pb(-1) of data collected with the L3 detector during the final LEP run at centre-of-mass energies around 205 GeV and 207 GeV No deviation from the Standard Model expectation is observed. The full data sample of 713 pb(-1), collected above the Z resonance, is used to constrain the coefficients of anomalous quartic gauge boson couplings to: -0.02 GeV-2 < a(0)/Lambda(2) < 0.03 GeV-2, -0.07 GeV-2 < a(c)/Lambda(2) < 0.05 GeV-2, at 95% confidence level. (C) 2002 Elsevier Science B.V. All rights reserved.