Search prospects for resonant Higgs boson pair production in the $b\bar{b}b\bar{b}$ final state with large-radius jets from $pp$ collisions at the HL-LHC

This note presents a study of resonant Higgs boson pair production in the $b\bar{b}b\bar{b}$ final state with 3000 fb$^{-1}$ of $\sqrt{s} = 14$ TeV $pp$ collisions at the HL-LHC. Results are based on a combination of extrapolation from a search carried out with $\sqrt{s} = 13$ TeV data and smearing of particle-truth level Monte Carlo simulation for the Kaluza-Klein graviton signal and the dominant multijet background. The truth-based analysis emulates the ``boosted'' analysis in which each of the Higgs bosons decaying into a $b\bar{b}$ system is reconstructed as a large-radius jet. Upper limits on the cross section for $pp \to G_\mathrm{KK} \to HH \to b\bar{b}b\bar{b}$ are estimated to be in the range between 1.44 fb at a resonance mass of 1.0 TeV and 0.025 fb at 3.0 TeV, at the 95% confidence level.