Search for Resonant $WZ \rightarrow \ell\nu \ell^{\prime}\ell^{\prime}$ Production in Proton-Proton Collisions at $\mathbf{\sqrt{s} = 13}$ TeV with the ATLAS Detector

A search for a $WZ$ resonance, in the fully leptonic final state (electrons and muons), is performed using 139 fb$^{-1}$ of data collected at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The results are interpreted in terms of a singly-charged Higgs boson of the Georgi-Machacek model, produced by $WZ$-fusion, and of a Heavy Vector Triplet, with the resonance produced by $WZ$-fusion or the Drell-Yan process. No significant excess is observed over the Standard Model predictions and limits are set on the production cross-section times branching ratio as a function of the resonance mass for these processes.