Ablikim, M.Achasov, M. N.Adlarson, P.Ahmed, S.Albrecht, M.Amoroso, A.Çetin, Serkant Ali2024-07-182024-07-1820212470-00102470-0029https://doi.org/10.1103/PhysRevD.103.072006https://hdl.handle.net/11411/7662Using (1310.6 +/- 7.0) x 10(6) J/psi events acquired with the BESIII detector at the BEPCII storage rings, the decay eta' -> pi(+)pi(-)mu(+)mu(-) is observed for the first time with a significance of 8 sigma via the process J/psi -> gamma eta'. We measure the branching fraction of eta' -> pi(+)pi(-)mu(+)mu(-) to be B(eta' -> pi(+)pi(-)mu(+)mu(-)) = (1.97 +/- 0.33(stat) +/- 0.19(syst)) x 10(-5), where the first and second uncertainties are statistical and systematic, respectively.eninfo:eu-repo/semantics/openAccessArticle2-s2.0-8510548696910.1103/PhysRevD.103.0720067Q1103Q1WOS:000648578400001