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

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doi:10.1103/PhysRevLett.129.022002

Using a sample of about 10(10) J/Psi events collected at a center-of-mass energy root s = 3.097 GeV with the BESIII detector, the electromagnetic Dalitz decays J/Psi -> e(+)e(-) pi(+)pi(-) eta', with eta' -> gamma pi(+)pi(-) and eta' -> pi(+)pi(-) eta, have been studied. The decay J/Psi -> e(+)e(-) X(1835) is observed with a significance of 15 sigma, and also an e(+)e(-) invariant-mass dependent transition form factor of J/Psi -> e(+)e(-) X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the pi(+)pi(-) eta' invariant-mass spectrum with significances of 5.3 sigma and 7.3 sigma. The corresponding product branching fractions for J/Psi -> e(+)e(-) X, X -> pi(+) pi(-) eta' [X = X(1835), X(2120), and X(2370)] are reported.