Bridging correlation and spectroscopy measurements to access the hadron interaction behind molecular states: The case of the Ξ(1620) and Ξ(1690) in the K−Λ system

Abstract

We study the compatibility between the K−Λ correlation function, recently measured by the ALICE collaboration, and the LHCb K−Λ invariant mass distribution obtained in the Ξb−→J/ψΛK− decay. The K−Λ invariant mass distribution associated with the Ξb− decay has been calculated within the framework of unitary effective field theories using two models, one of them constrained by the K−Λ correlation function. We consider two degenerate pentaquark Pcs states in the J/ψΛ scattering amplitude which allows us to investigate their impact on both the K−Λ and J/ψΛ mass distributions assuming different spin-parity quantum numbers and multiplicity. Without any fitting procedure, the K−Λ model is able to better reproduce the experimental K−Λ mass spectrum in the energy region above 1680 MeV as compared to previous unitarized scattering amplitudes constrained to a large amount of experimental data in the neutral S=−1 meson-baryon sector. We observe a tension between our model and the LHCb K−Λ distribution in the region close to threshold, largely dominated by the presence of the still poorly known Ξ(1620) state. We discuss in detail the different production mechanisms probed via femtoscopy and spectroscopy that could provide valid explanations for such disagreement, indicating the necessity to employ future correlation data in other S=−2 channels such as πΞ and K¯Σ. Published by the American Physical Society 2025