Aad, G.Abbott, B.Abbott, D.C.Abed Abud, A.Abeling, K.Abhayasinghe, D.K.Abidi, S.H.AbouZeid, O.S.Abraham, N.L.Abramowicz, H.Abreu, H.Abulaiti, Y.Abusleme Hoffman, A.C.Acharya, B.S.Achkar, B.Adam, L.Adam Bourdarios, C.Adamczyk, L.Adamek, L.Adelman, J.et al.2021-09-022021-09-022021Physics Letters B, 2021; 819:136412-1-136412-220370-26931873-2445http://hdl.handle.net/2440/131830A search for the Higgs boson decaying into a photon and a pair of electrons or muons with an invariant mass mll<30 GeV is presented. The analysis is performed using 139 fb−1of proton–proton collision data, produced by the LHC at a centre-of-mass energy of 13 TeV and collected by the ATLAS experiment. Evidence for the H→ll γprocess is found with a significance of 3.2 over the background-only hypothesis, compared to an expected significance of 2.1 for the Standard Model prediction. The best-fit value of the signal-strength parameter, defined as the ratio of the observed signal yield to the one expected in the Standard Model, is μ =1.5 ±0.5. The Higgs boson production cross-section times the H→llγbranching ratio for mll<30 GeV is determined to be 8.7+2.8−2.7fben©2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAPJournal article100004196010.1016/j.physletb.2021.1364120006792592000332-s2.0-85110648956571949Jackson, P. [0000-0002-0847-402X]Kong, A.X.Y. [0000-0001-8063-8765]McDougall, A.E. [0000-0001-7713-2800]Oliver, J.L. [0000-0002-0713-6627]Potti, H. [0000-0002-0800-9902]Ruggeri, T.A. [0000-0001-9941-1966]White, M.J. [0000-0001-5474-4580]