p ̄ final-state interaction in the reactions e⁺e⁻ → K⁻ p ̄ and J/ψ → K⁻ p ̄

Near-threshold pΛ ̄ p Λ ¯ mass spectra for the reactions e⁺e⁻ → K⁻ pΛ ̄ e + e - → K - p Λ ¯ and J/ψ → K⁻ pΛ ̄ J / ψ → K - p Λ ¯ are investigated with an emphasis on the role played by the interaction in the pΛ ̄ p Λ ¯ system. As guideline for the pΛ ̄ p Λ ¯ interaction a variety of Λ Λ ̄ Λ Λ ¯ potential models is considered that have been established in the analysis of data on pp̄→ Λ Λ ̄ p p ¯ → Λ Λ ¯ in the past. Arguments why the properties of the pΛ ̄ p Λ ¯ and Λ Λ ̄ Λ Λ ¯ interactions can be expected to be very similar are provided. It is shown that the near-threshold enhancement in the invariant mass observed for the e⁺e⁻ e + e - reaction can be reproduced quantitatively by the assumed pΛ ̄ p Λ ¯ final-state interaction in the partial wave suggested by an amplitude analysis of the experiment. The effect of the pΛ ̄ p Λ ¯ final-state interaction in other decays is explored, including the recently measured reactions B⁻ → J/ψ \, p̄ Λ B - → J / ψ p ¯ Λ and B⁺ → J/ψ \, p Λ ̄ B + → J / ψ p Λ ¯ . It is found that the final-state interaction improves the description of the measured invariant mass near threshold in most cases.