Aad, G.Aakvaag, E.Abbott, B.Abdelhameed, S.Abeling, K.Abicht, N.J.Abidi, S.H.Aboelela, M.Aboulhorma, A.Abramowicz, H.Abreu, H.Abulaiti, Y.Acharya, B.S.Ackermann, A.Adam Bourdarios, C.Adamczyk, L.Addepalli, S.V.Addison, M.J.Adelman, J.Adiguzel, A.et al.2025-05-092025-05-092024Journal of High Energy Physics (JHEP), 2024; 2024(8):164-1-164-621029-8479https://hdl.handle.net/2440/144460A search is presented for non-resonant Higgs boson pair production, targeting the bbZZ, 4V (V = W or Z), V V τ τ , 4τ , γγV V and γγτ τ decay channels. Events are categorised based on the multiplicity of light charged leptons (electrons or muons), hadronically decaying tau leptons, and photons. The search is based on a data sample of proton-proton collisions at √ s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1 . No evidence of the signal is found and the observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 17 (11) times the Standard Model predicted cross-section at 95% confdence level under the background-only hypothesis. The observed (expected) constraints on the HHH coupling modifer, κλ, are determined to be −6.2 < κλ < 11.6 (−4.5 < κλ < 9.6) at 95% confdence level, assuming the Standard Model for the expected limits and that new physics would only afect κλ.enOpen Access, Copyright CERN, for the beneft of the ATLAS Collaboration. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.Higgs Physics; Hadron-Hadron ScatteringJournal article10.1007/jhep08(2024)164705152Jackson, P. [0000-0002-0847-402X]McDougall, A.E. [0000-0001-7713-2800]Potti, H. [0000-0002-0800-9902]Ting, E.X.L. [0000-0002-5886-6339]White, M.J. [0000-0001-5474-4580]