Observation of electroweak production of two jets in association with a $Z$-boson pair in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

This note reports on the observation of electroweak production of two jets in association with a $Z$-boson pair using 139 fb$^{-1}$ of $pp$ collision data at $\sqrt{s} =$ 13 TeV collected by the ATLAS detector at the LHC. Two different final states originating from the decays of the $Z$ boson pair, one containing four charged leptons, and the other two charged leptons and two neutrinos, are considered. A significant deviation from the background-only hypothesis is observed, which corresponds to a statistical significance of 5.5 $\sigma$. The observed excess is compatible with the electroweak production of two jets in association with a $Z$-boson pair. In addition, cross-sections for inclusive production of $ZZ$ plus two jets, as well as the observed signal strength of the EW production, are reported.