Speaker
Description
This study presents projection results for the search of non-resonant Higgs boson pair production via vector-boson fusion (VBF) in the boosted $HH \to b\bar{b}b\bar{b}$ final state, using the upgraded ATLAS detector at the High Luminosity LHC (HL-LHC). The analysis extends the latest Run 2 results obtained with 140 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}=13$ TeV to HL-LHC conditions at $\sqrt{s}=14$ TeV, exploring integrated luminosities up to 3000 fb$^{-1}$. The boosted topology, where each Higgs boson is reconstructed as a single large-radius jet, enhances sensitivity to the quartic Higgs-vector boson coupling modifier $\kappa_{2V}$. The extrapolation employs likelihood scans under multiple systematic uncertainty scenarios reflecting expected detector and theoretical improvements. For 3000 fb$^{-1}$, the 68% (95%) confidence interval for $\kappa_{2V}$ is expected to be [0.84, 1.19] ([0.75, 1.27]) in the baseline scenario, and [0.86, 1.17] ([0.79, 1.23]) when only statistical uncertainties are considered. Reducing background-related systematic uncertainties by a factor of four improves the 5$\sigma$ sensitivity region by up to 16%. Additionally, an enhancement of the Higgs-to-$b\bar{b}$ tagging efficiency from 0.6 to 0.9 reduces the $\kappa_{2V}$ interval width by approximately 20%. These results demonstrate that the boosted $HH$ VBF channel will play a key role in probing the Higgs self-interactions and quartic couplings with unprecedented precision at the HL-LHC.
