The electromagnetic form factors of the $\Lambda$ in the timelike region

TL;DR

This paper investigates the electromagnetic form factors of the Lambda hyperon in the timelike region near the production threshold, emphasizing the role of final state interactions and providing theoretical predictions aligned with experimental observations.

Contribution

It introduces a rigorous treatment of final state interactions using various potential models to accurately reproduce the near-threshold enhancement of the form factor.

Findings

Reproduces the near-threshold enhancement of the effective form factor.

Provides predictions for Lambda electromagnetic form factors G_M and G_E.

Analyzes spin-dependent observables like spin-correlation parameters.

Abstract

The reaction $e^+e^- \to \bar \Lambda \Lambda$ is investigated for energies close to the threshold. Specific emphasis is put on the role played by the interaction in the final $\bar \Lambda \Lambda$ system which is taken into account rigorously. For that interaction a variety of $\bar \Lambda \Lambda$ potential models is employed that have been constructed for the analysis of the reaction $\bar p p \to \bar \Lambda \Lambda$ in the past. The enhancement of the effective form factor for energies close to the $\bar \Lambda \Lambda$ threshold, seen in pertinent experiments, is reproduced. Predictions for the $\Lambda$ electromagnetic form factors $G_M$ and $G_E$ in the timelike region and for spin-dependent observables such as spin-correlation parameters are presented.