Search for pair production of boosted Higgs bosons via vector-boson fusion in the 𝑏̄𝑏𝑏̄𝑏 final state using 𝑝𝑝 collisions at √𝑠 = 13 TeV with the ATLAS detector

A search for Higgs boson pair production via vector-boson fusion is performed in the Lorentz-boosted regime, where a Higgs boson candidate is reconstructed as a single large-radius jet, using 140 fb−1 of proton–proton collision data at √𝑠 = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Only Higgs boson decays into bottom quark pairs are considered. The search is particularly sensitive to the quartic coupling between two vector bosons and two Higgs bosons relative to its Standard Model prediction, 𝜅2𝑉 . This study constrains 𝜅2𝑉 to 0.55 < 𝜅2𝑉 < 1.49 at the 95% confidence level. The value 𝜅2𝑉 = 0 is excluded with a significance of 3.8 standard
deviations with other Higgs boson couplings fixed to their Standard Model values. A search for new heavy spin-0 resonances that would mediate Higgs boson pair production via vector-boson fusion is carried out in the mass range of 1–5 TeV for the first time under several model and decay-width assumptions. No significant deviation
from the Standard Model hypothesis is observed and exclusion limits at the 95% confidence level are derived.