Iro Koletsou – HDR’s defense – Dec. 20, 2023 – 14h

Vector boson scattering (VBS), VV → VV with V = W/Z/γ, is a key process for probing the SU(2)L×U(1)Y gauge symmetry of electroweak theory that determines the self-couplings of vector bosons. Rare and difficult to differentiate from its significant background background, it was only observed during Run 2 of the LHC. This manuscript traces the history of this discovery, from the first prospective analyzes to its study with an integrated luminosity of 139 fb-1 by the ATLAS collaboration. To begin, the experimental signature of the VBS process in the context of a hadronic collider is described, explaining the main challenges as well as the advantages and disadvantages of each diboson channel. Next, a very detailed critical analysis of the WZjj channel is presented, both for the study which led to its observation and for the study which led to the first measurements of differential cross sections and the interpretation of the results in the framework of Effective Field Theory. The status of other experimental channels is also presented and discussed briefly. Finally, the main items of Run 3 studies are highlighted, as well as the scientific objectives for the years to come.