Signal selection optimization for the Vector Fusion Category in the WZ $\rightarrow \ell \nu \ell \ell$ resonance search analysis performed in ATLAS at the LHC

The Standard Model of particle physics is currently the best model to describe the properties of elementary particles and their interaction with each other. Even if it has been confirmed by many experiments over and over, there are known physics phenomena that cannot be explained by the Standard Model and require an extension of the theory. Certain new physics models, with extended Higgs sectors, may hold answers to some long-lasting questions in particle physics, such as the origin of neutrino mass, the identity of dark matter, and the realization of a strong first-order phase transition for electroweak baryogenesis. The Georgi-Machacek model corresponds to such a benchmark model, which predicts a new resonance Higgs particle. In this work, the phase spaces of different variables are optimized for an exclusively leptonic decay channel in such a way that selection criteria are chosen with the aid of the significance. These are then validated by calculating the figures of merit. The selection criteria that are already used in the resonance analysis are first optimized by modifying the cut value for certain variables. If necessary, these will be adjusted and compared with the old values. Furthermore, some new discriminant variables are examined to see whether there is an equally good separation between background and signal regions possible. Finally, a new significance definition is used. Here it gets interesting whether the selection criteria are changing or whether this changes the figures of merit noticeable. The optimization takes place for the considered resonance process, but due to the similar behavior of the decay products, it can also be transferred to the Standard Model process of vector boson scattering.