Aad, G.Abbott, B.Abeling, K.Beddall, Andrew JohnÇetin, Serkant AliÖztürk, SertaçŞimşek, Sinem2025-04-182025-04-182024Null, N., Aad, G., Abbott, B., Abeling, K., Abicht, N., Abidi, S., ... & Balek, P. (2024). Search for short-and long-lived axion-like particles in $$ H\rightarrow aa\rightarrow 4\gamma $$ decays with the ATLAS experiment at the LHC. EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 84(7).14346044http://dx.doi.org/10.1140/epjc/s10052-024-12979-0https://hdl.handle.net/20.500.12713/7214Presented is the search for anomalous Higgs boson decays into two axion-like particles (ALPs) using the full Run 2 data set of 140fb-1 of proton-proton collisions at a centre-of-mass energy of 13TeV recorded by the ATLAS experiment. The ALPs are assumed to decay into two photons, providing sensitivity to recently proposed models that could explain the (g-2)μ discrepancy. This analysis covers an ALP mass range from 100 to 62GeV and ALP-photon couplings in the range 10-7TeV-1<Caγγ/Λ<1TeV-1, and therefore includes signatures with significantly displaced vertices and highly collinear photons. No significant excess of events above the Standard Model background is observed. Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to two ALPs in the four-photon final state, and are in the range of 10-5 to 3×10-2, depending on the hypothesized ALP mass and ALP-photon coupling strength.eninfo:eu-repo/semantics/openAccessArticle8471312-s2.0-8520002629910.1140/epjc/s10052-024-12979-0Q1