Searching for ttHH events with the ATLAS Experiment at the LHC

The Higgs self-coupling, which determines the shape of the Higgs potential, is one of the building blocks of the Standard Model of Particle Physics, directly connected to the electroweak symmetry breaking mechanism and to the stability of the Universe. In fact, probing the self-coupling is among the most important goals of the Particle Physics community and represents a key physics benchmark for the High-Luminosity phase of the Large Hadron Collider experiments. Searching for Higgs pair production constitutes a direct way to probe the Higgs self-coupling and a comprehensive research programme is ongoing in ATLAS to perform these analyses in Run 2 and Run 3 data. The production of a top quark-antiquark pair in association with a Higgs pair (ttHH) plays a special role in this context because, even if much rarer than the gluon fusion or Vector boson fusion production modes, is very sensitive to physics Beyond the Standard Model which predicts a quartic interaction between two top quarks and two Higgs bosons. My project was centered around the initial investigations of ttHH processes using ATLAS data, specifically focusing on the 4b decay mode of the two Higgs bosons. My efforts were primarily dedicated to developing the analysis framework by addressing its issues, and I also worked on improving the associated plotting tool. Additionally, I set up a deep neural network and conducted training thereof to differentiate between signal and background events.