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Abstract

Final states with multiple electroweak gauge bosons are important signatures for probing the non-Abelian character of the Standard Model SU(2)L x U(1)Y symmetry. The triple gauge boson production of Zγγ is measured in Run 2 of the LHC at a centre-of-mass energy of 13 TeV. The dataset contains pp collisions recorded with the ATLAS detector and corresponds to an integrated luminosity of 139 fb-1. The fully leptonic decay channel of the Z boson is analysed. Final state radiation is suppressed to obtain a pure sample of Zγγ events with prompt photons. The integrated cross section and differential cross sections of six kinematic observables are measured in a fiducial volume at particle-level, where the cross sections are corrected for detector effects. The results are compared to predictions of MC event generators at NLO QCD precision showing good agreement. The measurement with the highest sensitivity for new physics effects is used to constrain dimension-8 operators in an effective field theory approach. Existing constraints are improved by up to two orders of magnitude.