https://doi.org/10.1140/epja/s10050-021-00351-9
Regular Article – Theoretical Physics
Analysis of the 
reaction close to the threshold concerning claims of a 
state
1
Department of Physics, Guangxi Normal University, 541004, Guilin, China
2
School of Physics and Microelectronics, Zhengzhou University, 450001, Zhengzhou, Henan, China
3
Guangxi Key Laboratory of Nuclear Physics and Technology, Guangxi Normal University, 541004, Guilin, China
4
Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia - CSIC, Institutos de Investigación de Paterna, Aptdo. 22085, 46071, Valencia, Spain
Received:
17
July
2020
Accepted:
6
January
2021
Published online:
28
January
2021
We analyze the 
mass distribution from a recent Belle experiment on the 
reaction, and show that the mass distribution divided by phase space does not have a clear peak above the threshold that justifies the experimental claim of a state from those data. Then we use a unitary formalism with coupled channels 
, 
, 
, and 
, 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 amplitudes, some of them supporting a bound state and others not. The main conclusion is that the claim for the state, already included in the PDG, is premature, but refined data can provide very valuable information on the scattering amplitude. As side effects, we warn about the use of a Breit-Wigner amplitude parameterization close to threshold, and show that the channel plays an important role in this reaction.
© The Author(s) 2021
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