Search for Higgs Boson pair production in the two bottom quarks plus two photons final state in pp collisions at a centre-of-mass energy of 13 TeV with the ATLAS detector

This thesis presents a physics analysis performed with the ATLAS detector at the Large Hadron Collider with data from the Run 2 (2015-2018) period of proton-proton collision at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity used for physics analyses of 139 inverse-fb. The analysis is a search for resonant and non-resonant Higgs boson pair production in the two bottom quarks and two photon final state. Special focus is given to the event selection strategy for the resonant search using multi-variate techniques. In addition, the ATLAS upgrade for the Run 3 (2022-2025) period where the software is migrated to a multi-threading framework is extensively covered along with the new read-out upgrade for the High-Luminosity LHC that will be tested during Run 3.