Probing polarised production of two same-charge W bosons produced in association with two jets with the ATLAS detector

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Luka Nedic will use the data collected with the ATLAS detector at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) for his thesis. The ATLAS collaboration involves more than 4000 scientists, engineers, and students from hundreds of institutes in about 40 countries. His thesis will focus on studies of the production of two W bosons with the same charge in association with jets (ssWWjj) via vector boson scattering (VBS). Understanding this process first observed in 2018, and in particular the production of two longitudinally polarised W bosons in association with two jets (ssWWjj(LL), expected to be 5-7% of ssWWjj events), is a key test of the Standard Model and the mechanism of Electroweak Symmetry breaking. Luka Nedic will develop new methods to extract the small ssWWjj signal and increase the precision of differential cross-section measurements. Using machine learning tools for classification and regression, he will probe the production ssWWjj(LL) and perform first measurements of the polarisation fraction. He will also work towards extending the reach of the analysis by probing hadronically-decaying W bosons for the first time, further improving the sensitivity of the analysis. Luka Nedic will also contribute to the preparation of LHC Phase-II by participating in the effort conducted in the ATLAS Combined Performance group to update the offline software in preparation of the operation of the ATLAS Inner Tracker (ITk) upgrade. The completion of this task will lead to his qualification as an ATLAS author.