Observation and measurements of vector-boson scattering with the ATLAS experiment

The scattering of electroweak gauge bosons tests the gauge structure of the Standard Model and is sensitive to anomalous quartic gauge couplings. In this talk, recent results on vector-boson scattering from the ATLAS experiment using proton-proton collisions at $\sqrt{s}=13$ TeV are presented. These include the observation of $WZ$ and same-sign $WW$ production via vector-boson scattering along with studies of $VV$ production in semileptonic final states. Measurements of $ZZ$ production via vector-boson scattering are also presented. The measured cross sections are compared to theoretical predictions. The sensitivity of these predictions to the choices of renormalisation and factorisation scales, the Parton Distribution Functions and showering models is studied in detail for the case of electroweak scattering of two same-sign $W$ bosons in association with two jets and a number of event generator configurations are compared.