The Brout-Englert-Higgs mechanism is one of the main mechanisms of the Standard Model. It introduces a new field, the Higgs field, though which weak bosons become massive. This mechanism predicts also that the Higgs field can interact with itself. That means that the Higgs boson can decay into two Higgs bosons. Observing and measuring the Higgs-self-interaction would be the ultimate test of the theory of mass generation. Any deviation from Standard Model predictions would be a hint on new physics.
The challenge of this process is the low production rate, about 1000 times smaller than the single Higgs boson production. Also not all di-Higgs production occurs though Higgs self-coupling. This talk will review the recent results on the di-Higgs searches with the ATLAS detector and give an outlook on possible measurements at HL-LHC.