Search for ttH and tH production with $H \to \gamma \gamma$ at a center-of-mass energy of 13 TeV with the ATLAS Experiment

The measurement of the Yukawa coupling of the top quark is one important goal of particle physics after the discovery of the Higgs boson. There are two processes that offer the possibility to directly measure the Yukawa coupling of the top quark. These include the production of a top-antitop-quark pair in association with a Higgs boson via the strong interaction (ttH) and the electroweak production of a single top quark and a Higgs boson (tH). In the Standard Model, the cross section for tH production is much smaller than the cross section for ttH production as there is a destructive interference between diagrams where the Higgs boson is radiated from a top quark and diagrams where is it radiated from a W boson. But in contrast to ttH, this interference provides additional sensitivity to the sign of the Yukawa coupling. The considered Higgs boson decay into photons is promising due to the good energy resolution of the photons and the relatively small backgrounds. But it is also challenging due to the small branching ratio. The analysis strategy and the latest results on the search for ttH/tH production in the diphoton channel at the ATLAS experiment will be presented.