Search for Higgs Boson pair production in the final state with two bottom quarks and two photons in pp collisions at \sqrt{s} = 13 TeV with the ATLAS detector

In 2012, the ATLAS and CMS experiments jointly discovered the Higgs boson, a key particle of the Standard Model of particle physics. Since the discovery studies carry on, in order to measure the different properties of the Higgs Boson. These measurements provide information about the structure of the Higgs potential and test the standard model. One of the fundamental properties which is not measured yet is the trilinear coupling (or self-coupling) of the Higgs Bosons. An enhancement of the Higgs boson pair production with respect to the standard model would lead to new physics beyond-the-Standard-Model and could give an explanation of the baryogenesis. This discovery also raised new questions, in particular about the mass hierarchy. The existence of new particles could help answering this problem, a Higgs-like resonance being one of them. Various theories beyond the Standard Model predict the existence of such new scalar particles that can decay in two Higgs bosons. Among the different decay channels, the decay of the first Higgs boson into a pair of photons and the second Higgs boson into a pair of b-quark is one of the most promising since it benefits from the good diphoton resolution for the first one and the high branching ratio of the second one. In this talk I will present this search with 139 fb^{-1} of data collected by the ATLAS detector in 2015-2018. No excess with respect to background expectations are found and upper limits at 95% confidence level are set on the di-Higgs production cross sections and the Higgs trilinear coupling modifier. Limits on the production cross-section for a new particle over the mass range 251 GeV <= Mx <= 1000 GeV are set, improving up to a factor five the expected limit of the 36 fb-1 result.