Hayrapetyan, A.Tumasyan, A.Adam, W.Andrejkovic, J. W.Bergauer, T.Chatterjee, S.Damanakis, K.2025-03-232025-03-2320242470-00102470-0029https://doi.org/10.1103/PhysRevD.109.L111101https://hdl.handle.net/11486/5570The J/psi -> mu(+)mu(-)mu(+)mu(-) decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6 fb(-1). Normalizing to the J/psi -> mu(+)mu(-) decay mode leads to a branching fraction of [10.1(-2.7)(+3.3)(stat) +/- 0.4(syst)] x 10(-7), a value that is consistent with the standard model prediction.eninfo:eu-repo/semantics/openAccessArticle1091110.1103/PhysRevD.109.L1111012-s2.0-85195858537Q1WOS:001252843500001Q1