Aad, G.Abbott, B.Abdallah, J.Abdel Khalek, S.Abdinov, O.Aben, R.Abi, B.Abolins, M.Abouzeid, O.Abramowicz, H.Abreu, H.Abreu, R.Abulaiti, Y.Acharya, B.Adamczyk, L.Adams, D.Adelman, J.Adomeit, S.Adye, T.Agatonovic-Jovin, T.et al.2016-11-032016-11-032015Physical Review Letters, 2015; 114(8):081802-1-081802-190031-90071079-7114http://hdl.handle.net/2440/102206Searches are performed for resonant and nonresonant Higgs boson pair production in the γγbb¯ final state using 20 fb⁻¹ of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X → hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.en© 2015 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.(ATLAS Collaboration)Journal article003002433710.1103/PhysRevLett.114.0818020003502106000042-s2.0-84924362886169882