Evidence of ZZγ Production and Observation of 4ℓγ in Proton-Proton Collisions at s=13 TeV

Why this matters The key point is that CMS is reporting evidence for \(ZZ\gamma\) production for the first time in CMS. The 3.7σ result is conventionally described as evidence, rather than a 5σ observation. The separate inclusive \(4\ell\gamma\) analysis reaches 5.0σ, but that is a broader final state that includes final-state radiation and should not be interpreted as a 5σ observation of the specifically defined \(ZZ\gamma\) production process. In one sentence: CMS has found statistically significant evidence for producing two \(Z\) bosons and a photon in proton–proton collisions, with a measured rate broadly consistent with Standard Model expectations.