Search for new heavy resonances decaying to two Standard Model bosons with semi-leptonic final states using the full Run 2 ATLAS dataset

We present preliminary results of a combined search for new particles decaying to a vector boson and a Higgs boson, as well as to two vector bosons, focusing on semi-leptonic final states and using 139 fb$^{-1}$ of proton-proton collisions at the LHC. Two important models that predict such particles are the Heavy Vector Triplet (HVT) model and the two-Higgs-doublet model (2HDM), which address important deficiencies of the Standard Model related to the Higgs sector: the naturalness problem and the possibility of an extended scalar sector. The analysis will set limits on the production cross-sections of a new heavy vector boson predicted by the HVT model and of a new pseudoscalar boson A predicted by the 2HDM model, as well as constrain the respective models' parameters. Improvements in sensitivity with respect to previous iterations of the analysis using novel deep learning techniques will be discussed, with particular focus on a multi-class boosted jet classifier for the identification of the particle origin of the hadronic decay as coming from a top quark, a W boson, a Z boson, a Higgs boson, or multi-jet production.