$$\varLambda {\bar{\varLambda }}$$ final-state interaction in the reactions $$e^+e^- \rightarrow \phi {\varLambda }{\bar{{\varLambda }}}$$ and $$e^+e^- \rightarrow \eta {\varLambda }{\bar{{\varLambda }}}$$

Abstract

AbstractNear-threshold $$\varLambda {\bar{\varLambda }}$$ Λ Λ ¯ mass spectra for the reactions $$e^+e^- \rightarrow \eta \varLambda {\bar{\varLambda }}$$ e + e - → η Λ Λ ¯ and $$e^+e^- \rightarrow \phi \varLambda {\bar{\varLambda }}$$ e + e - → ϕ Λ Λ ¯ are investigated with an emphasis on the role played by the interaction in the $$\varLambda {\bar{\varLambda }}$$ Λ Λ ¯ system. A variety of $$\varLambda {\bar{\varLambda }}$$ Λ Λ ¯ potential models is employed that have been established in the analysis of data on $$p{\bar{p}}\rightarrow \varLambda {\bar{\varLambda }}$$ p p ¯ → Λ Λ ¯ in the past. It is shown that the near-threshold enhancement observed for the two $$e^+e^-$$ e + e - reactions can be reproduced by considering the $$\varLambda {\bar{\varLambda }}$$ Λ Λ ¯ final-state interaction in the partial waves suggested by the helicity-angle analysis of the experiments. For $$e^+e^- \rightarrow \eta \varLambda {\bar{\varLambda }}$$ e + e - → η Λ Λ ¯ the same $$\varLambda {\bar{\varLambda }}$$ Λ Λ ¯ S-wave interaction as in $$e^+e^- \rightarrow \varLambda {\bar{\varLambda }}$$ e + e - → Λ Λ ¯ is relevant and with it a consistent description of the pertinent measurements can be achieved. It is pointed out that a nonzero threshold cross section as observed for the latter reaction is not supported by the new $$\eta \varLambda {\bar{\varLambda }}$$ η Λ Λ ¯ data.