We search for new massive scalar particles Xand Ythrough the resonant process X→YH→b ̄bb ̄b, where His the standard model Higgs boson. Data from CERN LHC proton-proton collisions are used, collected at a centre-of-mass energy of 13TeVin 2016–2018 and corresponding to an integrated luminosity of 138fb−1. The search is performed in mass ranges of 0.9–4TeVfor Xand 60–600GeVfor Y, where both Yand Hare reconstructed as Lorentz-boosted single large-area jets. The results are interpreted in the context of the next-to-minimal supersymmetric standard model and also in an extension of the standard model with two additional singlet scalar fields. The 95% confidence level upper limits for the production cross section vary between 0.1 and 150fbdepending on the X and Y masses, and represent a significant improvement over results from previous searches.
