Eur. Phys. J. A (2023) 59: 136
https://doi.org/10.1140/epja/s10050-023-01017-4

Regular Article - Theoretical Physics

$\Lambda \overline{\Lambda }$ final-state interaction in the reactions $e^{+}{e}^{-}\to \varphi \Lambda \overline{\Lambda }$ and $e^{+}{e}^{-}\to \eta \Lambda \overline{\Lambda }$

¹ Institute for Advanced Simulation (IAS-4), Institut für Kernphysik (IKP-3) and Jülich Center for Hadron Physics, Forschungszentrum Jülich, 52428, Jülich, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany

^a j.haidenbauer@fz-juelich.de

Received: 16 March 2023
Accepted: 23 April 2023
Published online: 22 June 2023

Abstract

Near-threshold $\Lambda \overline{\Lambda }$ mass spectra for the reactions $e^{+}{e}^{-}\to \eta \Lambda \overline{\Lambda }$ and $e^{+}{e}^{-}\to \varphi \Lambda \overline{\Lambda }$ are investigated with an emphasis on the role played by the interaction in the $\Lambda \overline{\Lambda }$ system. A variety of $\Lambda \overline{\Lambda }$ potential models is employed that have been established in the analysis of data on $p\overline{p}\to \Lambda \overline{\Lambda }$ in the past. It is shown that the near-threshold enhancement observed for the two $e^{+}{e}^{-}$ reactions can be reproduced by considering the $\Lambda \overline{\Lambda }$ final-state interaction in the partial waves suggested by the helicity-angle analysis of the experiments. For $e^{+}{e}^{-}\to \eta \Lambda \overline{\Lambda }$ the same $\Lambda \overline{\Lambda }$S-wave interaction as in $e^{+}{e}^{-}\to \Lambda \overline{\Lambda }$ 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 $\eta \Lambda \overline{\Lambda }$ data.