$p\barΛ$ final-state interaction in the reactions $e^+e^- \to K^- p \bar Λ$ and $J/ψ\to K^- p \bar Λ$

Abstract

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