A Search for the Production of Pairs of Higgs Bosons Decaying to Four Bottom Quarks with the ATLAS Detector Using $\sqrt{s}=13$ TeV Proton-Proton Collisions at the Large Hadron Collider

A search for non-resonant Higgs boson pair production in the $b\overline{b}b\overline{b}$ final state is presented. The analysis uses up to 139 fb$^{-1}$ of pp collision data at $\sqrt{s} = 13$ TeV collected with the ATLAS detector. The analysis targets Higgs boson pairs produced via gluon-gluon fusion including a diagram involving the Higgs self-coupling and decaying into four resolved b-tagged jets. The observed data are consistent with Standard Model predictions. A 95% confidence upper limit on the standard model cross-section is set at 284 fb, and the trilinear Higgs self-coupling parameter is constrained to $\lambda_{hhh} \in [-5.5\lambda_{\text{SM}}, 12.7\lambda_{\text{SM}}]$ at 95% confidence, assuming Standard Model values for all other couplings.