Abstract

A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb(-1) of pp collision data at root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: b (b) over barb (b) over bar, (b) over barb tau(+)tau(-), and b (b) over bar gamma gamma. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating fromthe decay of a narrowscalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches.