Analysis of the e+e-→J/ψDD¯ reaction close to the threshold concerning claims of a χc0(2P) state

• Published in: The European physical journal. A, Hadrons and nuclei Hadrons and nuclei, 2021, Vol.57 (1)
• Main Authors: Wang, En, Liang, Wei-Hong, Oset, Eulogio
• Format: Article
• Language: English
• Subjects: Hadrons; Heavy Ions; Mass distribution; Nuclear Fusion; Nuclear Physics; Parameterization; Particle and Nuclear Physics; Physics; Physics and Astronomy; Regular Article – Theoretical Physics; Scattering amplitude; Side effects
• ISSN: 1434-6001; 1434-601X
• DOI: 10.1140/epja/s10050-021-00351-9

We analyze the D D ¯ mass distribution from a recent Belle experiment on the e + e - → J / ψ D D ¯ reaction, and show that the mass distribution divided by phase space does not have a clear peak above the D D ¯ threshold that justifies the experimental claim of a χ c 0 ( 2 P ) state from those data. Then we use a unitary formalism with coupled channels D + D - , D 0 D ¯ 0 , D s D ¯ s , and η η , with some of the interactions taken from a theoretical model, and use the data to fix other parameters. We then show that, given the poor quality of the data, we can get different fits leading to very different D D ¯ amplitudes, some of them supporting a D D ¯ bound state and others not. The main conclusion is that the claim for the χ c 0 ( 2 P ) state, already included in the PDG, is premature, but refined data can provide very valuable information on the D D ¯ scattering amplitude. As side effects, we warn about the use of a Breit-Wigner amplitude parameterization close to threshold, and show that the D s D ¯ s channel plays an important role in this reaction.