Triangle singularity in the K⁻d → pΣ⁻ reaction and its relevance to find the K̅N amplitude below threshold

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 Rez, Czech Republic
³ School of Science, Huzhou University, Huzhou 313000, Zhejiang, China

^* e-mail: Eulogio.Oset@ific.uv.es
^** e-mail: Raquel.Molina@ific.uv.es
^*** e-mail: dailianrong@zjhu.edu.cn
^**** e-mail: edfeijoo@ific.uv.es

Published online: 9 November 2022

Abstract

We study for the first time the pΣ⁻ → K⁻d and its time reversal reaction close to threshold and show that they are driven by a triangle mechanism, with the Λ(1405), a proton and a neutron as intermediate states, which develops a triangle singularity close to the K̅d threshold. As the main result, we find that the cross section, well within measurable range, is very sensitive to different models that, while reproducing K̅N observables above threshold, provide different extrapolations of the K̅N amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the K̅N amplitudes below threshold and to more accurate predictions of the Λ(1405) state of lower mass.