Measurement of $Z\gamma\gamma$ production in $pp$ collisions at $\sqrt{s}= 13$ TeV with the ATLAS detector

The collaboration
CERN-EP-2022-192, 2022.

Abstract (data abstract)
CERN-LHC. Cross-sections for the production of a $Z$ boson in association with two photons are measured in proton-proton collisions at a centre-of-mass energy of $13 \, \mathrm{TeV}$. The data used correspond to an integrated luminosity of $139 \, \mathrm{fb}^{-1}$ recorded by the ATLAS experiment during Run 2 of the LHC. The measurements use the electron and muon decay channels of the $Z$ boson, and a fiducial phase-space region where the photons are not radiated from the leptons. The integrated $Z(\rightarrow\ell\ell)\gamma\gamma$ cross-section is measured with a precision of $12\%$ and differential cross-sections are measured as a function of six kinematic variables of the $Z\gamma\gamma$ system. The data are compared with predictions from MC event generators which are accurate to up to next-to-leading order in QCD. The cross-section measurements are used to set limits on the coupling strengths of dimension-8 operators in the framework of an effective field theory.