The e + e - →Zγγ→qq̅γγ reaction at LEP and constraints on anomalous quartic gauge boson couplings

Abstract The cross section of the process e + e − → Z γ γ → q q ¯ γ γ 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 / Λ 2 0.03 GeV − 2 , − 0.07 GeV − 2 a c / Λ 2 0.05 GeV − 2 , at 95% confidence level.