Vector Boson Scattering and ZZ Production at ATLAS Detector

This work focuses on the search for electroweak production of two $Z$ bosons accompanied by a pair of jets in proton-proton collisions with the ATLAS detector at the LHC in CERN. The effort aspires to be a basis for further research of vector boson scattering phenomena with two $Z$ bosons decaying into charged leptons in the final state. The search exploits ATLAS proton-proton collision data corresponding to 139 fb$^{-1}$ of integrated luminosity, acquired at 13 TeV center-of-mass energy in proton-proton collisions during the Run 2 period of LHC. The background-only hypothesis is excluded with statistical significance of 5.8 $\sigma$, and the fiducial $ZZjj$ EW production cross-section is measured to be $\sigma_\text{EW} = 0.36 ^{+0.09}_{-0.09} \mathrm{(stat.)} ^{+0.05}_{-0.05} \mathrm{(syst.)} \text{fb}$, with no significant deviation from the standard model prediction. It makes the measurement, together with simultaneous independent results from the ATLAS and CMS experiments [Aad:2020zbq,Sirunyan:2020alo], the first observation of electroweak production of two Z bosons in the four-lepton channel.