Search for a massive scalar resonance decaying to a light scalar and a Higgs boson in the four b quark final state with boosted topology

We search for the resonant production of a new massive scalar X decaying into a new light scalar Y and the standard model Higgs boson H through the process $\text{X}\!\!\to\!\!\text{Y}\text{H}\!\!\to\!\!\text{b}\overline{\text{b}}\text{b}\overline{\text{b}}$. The search uses proton-proton collision data from the CERN LHC, collected at a centre-of-mass energy of 13 TeV in 2016-2018 and corresponding to an integrated luminosity of 138 fb$^{-1}$. The search is dedicated to mass ranges of X (0.9-4 TeV) and Y (60-600 GeV) where both the Y and the H are highly Lorentz-boosted and therefore their b quark-antiquark daughter particles are sufficiently collimated to be reconstructed using single large-area jets each. The mass of the one of the jets is required to be compatible with that of the Higgs boson, which is 125 GeV. A scan is performed in a two dimensional phase space spanned by the mass of the other jet, associated with Y, and the invariant mass of the two jets used to reconstruct X. The results are interpreted in the context of scalar resonances predicted in the next-to-minimal supersymmetric standard model and upper limits are placed on the production cross section as a function of the masses of X and Y. This is the first search for this process using Lorentz-boosted event topologies and it significantly extends the constraints on the model under consideration.