Search for pair production of Higgs bosons in the $b\bar{b}b\bar{b}$ final state using proton-proton collisions at 13 TeV with the ATLAS detector

A search for Higgs-boson pair production in the $b\bar{b}b\bar{b}$ final state is carried out with 13.3 ~$fb^{-1}$ of LHC proton-proton collision data collected at $\sqrt{s} = 13$ TeV with the ATLAS detector in 2015 and 2016. The data are consistent with the estimated background and are used to set upper limits on the production cross section of Higgs-boson pairs times branching ratio to $b\bar{b}b\bar{b}$ for both non-resonant and resonant production. In the context of the Randall--Sundrum model, upper limits in the 1000 fb to 2 fb range are obtained for masses between 300 and 3000 GeV, at the 95% confidence level. The cross section times branching ratio for non-resonant Standard Model Higgs-boson pair production is constrained to be less than 330 fb, 29 times the Standard Model predicted cross section of $11.3^{+0.9}_{-1.0}$ fb.