Observation of J /? Electromagnetic Dalitz Decays to X (1835), X (2120), and X (2370)

Abstract

Abstract: Using a sample of about 1010 J/? events collected at a center-of-mass energy s=3.097 GeV with the BESIII detector, the electromagnetic Dalitz decays J/??e+e-?+?-??, with ?????+?- and ????+?-?, have been studied. The decay J/??e+e-X(1835) is observed with a significance of 15?, and also an e+e- invariant-mass dependent transition form factor of J/??e+e-X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the ?+?-?? invariant-mass spectrum with significances of 5.3? and 7.3?. The corresponding product branching fractions for J/??e+e-X, X??+?-?? [X=X(1835), X(2120), and X(2370)] are reported. © 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.