Invariant-mass spectrum of $\Lambda\bar\Lambda$ pair in the process $e^+e^-\rightarrow\phi\Lambda\bar\Lambda$

TL;DR

This paper demonstrates that the near-threshold invariant-mass spectrum of b3b4 in the process
d+e- bb b3b4 can be explained by final-state interactions, with a simple potential model fitting recent experimental data.

Contribution

The study provides a simple two-parameter potential model that explains the invariant-mass spectrum and clarifies the quantum numbers of the b3b4 pair.

Findings

The peak position is above the threshold despite attractive interaction.

The spectrum aligns with quantum numbers 1^{++} and 2^{++}.

The spectrum contradicts the 2^{-+} assignment.

Abstract

We show that the final-state interaction perfectly explains the recent experimental data of BESIII Collaboration on the near-threshold invariant-mass spectrum of $\Lambda\bar\Lambda$ in the process $e^+e^-\rightarrow\phi\Lambda\bar\Lambda$. The position of peak in invariant-mass spectrum is above the threshold though the interaction of $\Lambda$ and $\bar\Lambda$ is due to an attractive potential. This potential has a simple form and depends only on two parameters. We show that the invariant-mass spectrum is consistent with the quantum numbers $J^{PC}=1^{++}$ and $2^{++}$ of $\Lambda\bar\Lambda$ pair but contradicts to $J^{PC}=2^{-+}$.