The angular separation between the photon and the lepton ${\ensuremath{\Delta R}\xspace}(\gamma,\mathrm{lepton})$ is required to be greater than 0.35. Electrons must satisfy a set of loose requirements as described in Ref. [@CMS-DP-2015-067] and they are not selected in the pseudorapidity region $1.4442<\abs{\eta}<1.566$. Furthermore, the invariant mass of the candidate electron and either of the two photons is required to be at least $5$from the nominal boson mass, in order to reject $\cPZ+\Pgg\to\Pep\Pem\Pgg$ events with a misidentified electron. Muons are required to pass a tight selection based on the quality of the track fit, the number of associated hits in the tracking detectors, and the longitudinal and transverse impact parameters of the track with respect to the event vertex and to satisfy a requirement on the relative isolation, corrected for pileup effects, calculated as the sum of the transverse energy of charged hadrons, neutral hadrons and photons in a cone of radius $0.4$ around the muon. Generator-level leptons, required to satisfy the same kinematic selection, are “dressed”, , the four-momenta of all photons in a cone of radius ${\ensuremath{\Delta R}\xspace}=0.1$ around the lepton are added to the four-momentum of the lepton.

The identification and trigger efficiencies are measured using data events containing 