# Hadronic structure functions in the $e^+ e^- \rightarrow \bar{\Lambda} \Lambda$ reaction

## TL;DR

This paper calculates cross-section distributions for the e+ e- to Lambda hyperon pair production via J/psi decay, revealing how hyperon form factors influence decay distributions and how their properties can be experimentally determined.

## Contribution

It introduces a method to extract the size and phase of Lambda hyperon form factors from decay distributions in e+ e- annihilation reactions.

## Key findings

- Hyperon decay distributions depend on bilinear form factors.
- Relative phase and magnitude of form factors can be uniquely determined.
- Decay asymmetry parameters can be measured from joint decay distributions.

## Abstract

Cross-section distributions are calculated for the reaction $e^+ e^- \rightarrow J/\psi\rightarrow \bar{\Lambda}(\rightarrow \bar{p}\pi^+) \Lambda(\rightarrow p\pi^-)$, and related annihilation reactions mediated by vector mesons. The hyperon-decay distributions depend on a number of structure functions that are bilinear in the, possibly complex, psionic form factors $G_M^\psi$ and $G_E^\psi$ of the Lambda hyperon. The relative size and relative phase of these form factors can be uniquely determined from the unpolarized joint-decay distributions of the Lambda and anti-Lambda hyperons. Also the decay-asymmetry parameters of Lambda and anti-Lambda hyperons can be determined.