Recent measurements from the ATLAS experiment of Multi-Boson production processes at the LHC

Abstract: The high-energy proton-proton collisions at the Large Hadron Collider provide the ideal conditions to study the rare processes predicted by the Standard Model (SM) such as the production of multiple electroweak bosons. These processes involve the self-interactions of the gauge bosons through triple and quartic gauge couplings (TGCs and QGCs), in addition to interactions with the Higgs boson. Therefore, precision measurements of multi-boson final states probe the electroweak symmetry breaking mechanism and allow to search for deviations from the SM. Four recently published ATLAS results are summarised in this document. The first two results are measurements of the production of di-boson final states in association with jets: the observation of $WW/WZ/ZZ$ production in semileptonic final states is described, and a measurement of the polarisation states of same-sign $W$ pairs is also discussed. The second set of measurements are related to the triple production of electroweak bosons: the first analysis reports the observation of $WWγ$ in the leptonic final state, while the second result presents the observation of triple vector boson production where at least one of the produced bosons is a $Z$ boson. All the measurements use datasets collected at a centre-of-mass energy of 13~TeV and corresponding to an integrated luminosity of 140~fb$^{-1}$.