$$\varLambda (1405)$$ Λ ( 1405 ) mediated triangle singularity in the $$K^-d\rightarrow p\varSigma ^-$$ K - d → p Σ - reaction

Autor: A. Feijoo, R. Molina, L. R. Dai, Eulogio Oset
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: European Physical Journal C: Particles and Fields, Vol 82, Iss 11, Pp 1-16 (2022)
Druh dokumentu: article
ISSN: 1434-6052
DOI: 10.1140/epjc/s10052-022-10985-8
Popis: Abstract We study for the first time the $$p\varSigma ^-\rightarrow K^-d$$ p Σ - → K - d and $$K^-d\rightarrow p\varSigma ^-$$ K - d → p Σ - reactions close to threshold and show that they are driven by a triangle mechanism, with the $$\varLambda (1405)$$ Λ ( 1405 ) , a proton and a neutron as intermediate states, which develops a triangle singularity close to the $${\bar{K}}d$$ K ¯ d threshold. We find that a mechanism involving virtual pion exchange and the $$K^-p\rightarrow \pi ^+\varSigma ^-$$ K - p → π + Σ - amplitude dominates over another one involving kaon exchange and the $$K^-p\rightarrow K^-p$$ K - p → K - p amplitude. Moreover, of the two $$\varLambda (1405)$$ Λ ( 1405 ) 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 $${\bar{K}}N$$ K ¯ N observables above threshold, provide different extrapolations of the $${\bar{K}}N$$ K ¯ N amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the $${\bar{K}}N$$ K ¯ N amplitudes below threshold and to more accurate predictions of the $$\varLambda (1405)$$ Λ ( 1405 ) state of lower mass.
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