Search for di-boson resonances in the semileptonic final state in p- p collisions at √s = 13 TeV collected with the ATLAS detector

With the discovery of the Higgs boson by the ATLAS [1] and CMS [2] experiments at the LHC at CERN in 2012, the Standard Model is now complete, yet unanswered questions are still present. In example the Standard Model does not explain the hierarchy between the weak and Planck scales, nor it includes a dark matter candidate, nor it explain the origin of barion asymmetry. For this reason, one of the goals of particle physics research is to find new hints of physics beyond the Standard Model that could answer some of these questions. Analyses searching for di-boson resonances are a very powerful tool to investigate many beyond the Standard Model scenarios such as extension of the Higgs sector [3, 4], Heavy Vector triplets [5] (W′ and Z′ ) or excited states of Gravitons [6, 7]. These searches exploit many decay channels of the two bosons allowing to select topologies with varied signal to background ratios and statistics. This thesis describes the search for new resonances decaying to a pair of massive vector bosons (X → WW, W Z) in a 36.1 fb$^{-1}$ data sample of proton-proton collisions produced at a centre-of-mass energy of √s = 13TeV collected with the ATLAS detector. The final state is reconstructed through the semi-leptonic decays ℓνqq (ℓ = e, µ) of the two vector bosons.