Ablikim, M.Achasov, M.N.Adlarson, P.Albrecht, M.Çetin, Serkant AliKolcu, Onur Buğra2022-07-252022-07-252022Ablikim, M., Achasov, M. N., Adlarson, P., Albrecht, M., Aliberti, R., Amoroso, A., ... & Kalantar-Nayestanaki, N. (2022). Observation of the double Dalitz decay $\eta'\to e^+ e^-e^+ e^-$. arXiv preprint arXiv:2203.12229.2470-0010https://doi.org/10.1103/PhysRevD.105.112010https://hdl.handle.net/20.500.12713/3042Based on (10087±44)×106 J/? events collected with the BESIII detector at BEPCII, the double Dalitz decay ???e+e-e+e-is observed for the first time via the J/????? decay process. The significance is found to be 5.7? with systematic uncertainties taken into consideration. Its branching fraction is determined to be B(???e+e-e+e-)=(4.5±1.0(stat)±0.5(sys))×10-6. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.eninfo:eu-repo/semantics/openAccessArticle10511WOS:0008269699000052-s2.0-85134244532Q110.1103/PhysRevD.105.112010Q1