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Using 9. 0 fb^-1 of e^+e^- collision data collected at center-of-mass energies from 4. 178 to 4. 278 GeV with the BESIII detector at the BEPCII collider, we perform the first search for the radiative transition ₂₁ (3872) ₂ (3823). No ₂₁ (3872) ₂ (3823) signal is observed. The upper limit on the ratio of branching fractions B (₂₁ (3872) ₂ (3823), ₂ (3823) ₂₁) /B (₂₁ (3872) ^+^- J/) is set as 0. 075 at the 90\% confidence level. Our result contradicts theoretical predictions under the assumption that the ₂₁ (3872) is the pure charmonium state ₂₁ (2P).
Collaboration et al. (2024) studied this question.