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Using (27. 12 0. 14) 10^8 (3686) events collected with the BESIII detector, we present the first observation of the decays ₂₉, where J=0, 1, 2, with statistical significances of 11. 7, 11. 2, and 11. 8. The branching fractions of these decays are determined to be B (₂₀) = (2. 37 0. 22 0. 23) 10^-4, B (₂₁) = (1. 01 0. 10 0. 11) 10^-4, and B (₂₂) = (1. 40 0. 13 0. 17) 10^-4, where the first uncertainties are statistical and the second are systematic. We observe no clear intermediate structures.
Collaboration et al. (Tue,) studied this question.