2023/05/18 by Takuma Nishibuchi, Tetsuo Hyodo, Nishibuchi, Takuma +1
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Nuclear Theory (nucl-th) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2305.10753
openalex publication_date 2023/05/18 · openalex created_date 2023/05/21 · openalex updated_date 2026/07/28
We study the Ξ(1620) resonance near the KΛ threshold in the light of the recent experimental constraints. The Belle collaboration have found a resonance peak of Ξ(1620) slightly below the K0Λ threshold in the π+Ξ- invariant mass spectrum, and the ALICE collaboration have determined the K-Λ scattering length from the measurement of the momentum correlation functions in the heavy ion collisions. Using the effective range expansion, we classify the nature of the pole of the near-threshold eigenstate in terms of the scattering length, in the presence of the decay channel. It is shown that the quasibound state below the threshold can be described by only the scattering length, while the description of the resonance above the threshold requires the contribution from the effective range. Based on the chiral unitary approach, we construct a theoretical model which generates the pole of Ξ(1620) below the KΛ threshold with relatively narrow width, as reported by the Belle collaboration. It is quantitatively demonstrated that the spectrum of the Ξ(1620) quasibound state is distorted by the effect of the nearby KΛ threshold. We then construct another model which reproduces the K-Λ scattering length by the ALICE collaboration. In this case, the eigenstate pole does not appear in the physically relevant Riemann sheets, and the spectrum shows a cusp structure at the KΛ threshold. We finally examine the compatibility of the value of the KΛ scattering length and the subthreshold pole of Ξ(1620) including the experimental uncertainties.