https://doi.org/10.1140/epjc/s10052-022-10985-8
Regular Article - Theoretical Physics
mediated triangle singularity in the 
reaction
1
Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigación de Paterna, Aptdo. 22085, 46071, Valencia, Spain
2
Nuclear Physics Institute, 25068, Řež, Czech Republic
3
School of Science, Huzhou University, 313000, Huzhou, Zhejiang, China
Received:
8
June
2022
Accepted:
1
November
2022
Published online:
15
November
2022
We study for the first time the 
and reactions close to threshold and show that they are driven by a triangle mechanism, with the , a proton and a neutron as intermediate states, which develops a triangle singularity close to the 
threshold. We find that a mechanism involving virtual pion exchange and the 
amplitude dominates over another one involving kaon exchange and the 
amplitude. Moreover, of the two states, the one with higher mass around 1420 MeV, gives the largest contribution to the process. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing 
observables above threshold, provide different extrapolations of the amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the amplitudes below threshold and to more accurate predictions of the state of lower mass.
© The Author(s) 2022
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