Search for resonant pair production of Higgs bosons in the bbbb final state using large-area jets in proton-proton collisions at s = 13 TeV

A search is presented for the resonant production of a pair of standard model-like Higgs bosons using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016-2018, corresponding to an integrated luminosity of 138 fb^-1. The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where at least one of the pairs is highly Lorentz-boosted and is reconstructed as a single large-area jet. The other pair may be either similarly merged or resolved, the latter reconstructed using two b-tagged jets. The data are found to be consistent with standard model processes and are interpreted as 95% confidence level upper limits on the product of the cross sections and the branching fractions of the spin-0 radion and the spin-2 bulk graviton that arise in warped extradimensional models. The limits set are in the range 9. 74-0. 29 fb and 4. 94-0. 19 fb for a narrow radion and a graviton, respectively, with masses between 1 and 3 TeV. For a radion and for a bulk graviton with widths 10% of their masses, the limits are in the range 12. 5-0. 35 fb and 8. 23-0. 23 fb, respectively, for the same masses. These limits result in the exclusion of a narrow-width graviton with a mass below 1. 2 TeV, and of narrow and 10%-width radions with masses below 2. 6, and 2. 9 TeV, respectively.