Ablikim, M.Achasov, M.N.Adlarson, P.Ai, X.C.Aliberti, R.Amoroso, A.Çetin, Serkant Ali2024-05-192024-05-1920242470-0010https://doi.org/10.1103/PhysRevD.109.032006https://hdl.handle.net/20.500.12713/4518Using a sample of 10 billion J/? events collected with the BESIII detector, the decays ????+?-?+?-, ????+?-?0?0 and ???4?0 are studied via the process J/?????. The branching fractions of ????+?-?+?- and ????+?-?0 ?0 are measured to be (8.56±0.25(stat)±0.23(syst))×10-5 and (2.12±0.12(stat)±0.10(syst))×10-4, respectively, which are consistent with previous measurements but with improved precision. No significant ???4?0 signal is observed, and the upper limit on the branching fraction of this decay is determined to be less than 1.24×10-5 at the 90% confidence level. In addition, an amplitude analysis of ????+?-?+?- is performed to extract the doubly virtual isovector form factor ? for the first time. The measured value of ?=1.22±0.33(stat)±0.04(syst), is in agreement with the prediction of the vector meson dominance model. © 2024 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/openAccessArticle10932-s2.0-8518576274510.1103/PhysRevD.109.032006Q1