Measurement of inclusive cross section and observation of electroweak production of two jets inassociation with a $Z$-boson pair in $pp$ collisions at√s=13TeV with the ATLAS detector

Abstract

The observation of electroweak production of two jets in association with a Z-boson pair using 139 fb−1 of pp collision data at √s = 13 TeV collected by the ATLAS detector at the LHC is presented. 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 σ. 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.