Using a sample of about 1010 J/ψ events collected at a center-of-mass energy s=3.097 GeV with the BESIII detector, the electromagnetic Dalitz decays J/ψ→e+e-π+π-η′, with η′→γπ+π- and η′→π+π-η, have been studied. The decay J/ψ→e+e-X(1835) is observed with a significance of 15σ, and also an e+e- invariant-mass dependent transition form factor of J/ψ→e+e-X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the π+π-η′ invariant-mass spectrum with significances of 5.3σ and 7.3σ. The corresponding product branching fractions for J/ψ→e+e-X, X→π+π-η′ [X=X(1835), X(2120), and X(2370)] are reported.
Предметные области OECD FOS+WOS
- 1.03 ФИЗИЧЕСКИЕ НАУКИ И АСТРОНОМИЯ