Projected sensitivity to non-resonant Higgs boson pair production in the $b\bar{b}b\bar{b}$ final state using proton–proton collisions at HL-LHC with the ATLAS detector

Estimates of the sensitivity to non-resonant Higgs boson pair production using the $HH\to b\bar{b}b\bar{b}$ channel with the full HL-LHC dataset of 3000 fb$^{-1}$ of proton--proton collisions at $\sqrt{s} = 14\,$TeV. These estimates are based on the extrapolation of current results obtained with the 2016 dataset, comprising $\int Ldt = 10.1\,$fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = 13\,$TeV. In the absence of any signal and without (with) systematics, cross-sections 1.5 times (5.2 times) greater than the Standard Model prediction are excluded at the 95% confidence level. The Higgs boson self-coupling, $\lambda_{HHH}$ can be constrained to $0.2 < \lambda_{HHH}/\lambda^{SM}_{HHH} < 7.0$ $(−3.5 < \lambda_{HHH}/\lambda^{SM}_{HHH} < 11)$. The sensitivity of the analysis to increasing trigger thresholds has been studied. The jet pT requirement of the projected High-Luminosity LHC trigger increases the cross-section limit by a factor 1.3 (2.2).