Aad, G.Aakvaag, E.Abbott, B.Abdelhameed, S.Abeling, K.Abicht, N.J.Abidi, S.H.Aboelela, M.Aboulhorma, A.Abramowicz, H.Abulaiti, Y.Acharya, B.S.Ackermann, A.Adam Bourdarios, C.Adamczyk, L.Addepalli, S.V.Addison, M.J.Adelman, J.Adiguzel, A.Adye, T.et al.2025-06-112025-06-112025Physical Review D (particles, fields, gravitation, and cosmology), 2025; 111(3):032006-1-032006-322470-00102470-0029https://hdl.handle.net/2440/145085A search for the production of three Higgs bosons (𝐻⁡𝐻⁡𝐻) in the 𝑏⁢ ¯ 𝑏 ⁢𝑏⁢ ¯ 𝑏 ⁢𝑏⁢ ¯ 𝑏 final state is presented. The search uses 126  fb−1 of proton-proton collision data at √𝑠 =13  TeV collected with the ATLAS detector at the Large Hadron Collider. The analysis targets both nonresonant and resonant production of 𝐻⁡𝐻⁡𝐻. The resonant interpretations primarily consider a cascade decay topology of 𝑋 →𝑆⁢𝐻 →𝐻⁡𝐻⁡𝐻 with masses of the new scalars 𝑋 and 𝑆 up to 1.5 and 1 TeV, respectively. In addition to scenarios where 𝑆 is off-shell, the nonresonant interpretation includes a search for Standard Model 𝐻⁡𝐻⁡𝐻 production, with limits on the trilinear and quartic Higgs self-coupling set. No evidence for 𝐻⁡𝐻⁡𝐻 production is observed. An upper limit of 59 fb is set, at the 95% confidence level, on the cross section for Standard Model 𝐻⁡𝐻⁡𝐻 production.en© 2025 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3 .triple Higgs boson production; ATLAS detectorJournal article10.1103/physrevd.111.032006729049Fewell, M.P. [0000-0002-4406-0430]Gallagher, J. [0000-0001-9284-6270]Jackson, P. [0000-0002-0847-402X]Kong, A.X.Y. [0000-0001-8063-8765]Pandya, H.D. [0000-0002-1199-945X]Potti, H. [0000-0002-0800-9902]Ruggeri, T.A. [0000-0001-9941-1966]Ting, E.X.L. [0000-0002-5886-6339]White, M.J. [0000-0001-5474-4580]