The electromagnetic form factors of $\Lambda$ hyperon in $e^+e^-\rightarrow \bar\Lambda\Lambda$

TL;DR

This paper models the electromagnetic form factors of the Lambda hyperon in electron-positron annihilation, fitting experimental data with a simple parametrization and predicting polarization observables.

Contribution

It introduces a pQCD-inspired two-parameter model for Lambda hyperon form factors and fits it to recent experimental data, providing predictions for polarization observables.

Findings

Successful fit to existing data outside threshold region

Reproduction of known form factor behavior

Predictions for spin polarization observables

Abstract

We study the electromagnetic form factors of $\Lambda$ hyperon in the timelike region using the recent experimental data in the exclusive production of $\bar{\Lambda} \Lambda$ pair in electron-position annihilation. We present a pQCD inspired parametrization of $G_E(s)$ and $G_M(s)$ with only two parameters, and we consider a suppression mechanism of the electric form factor $G_E(s)$ compared to the magnetic form factor $G_M(s)$. The parameters are determined through fitting our parametrization to the effective form factor data in the reaction $e^+e^-\rightarrow \bar\Lambda\Lambda$. Except the threshold region, our parametrization can reproduce satisfactorily the known behavior of the existing data from the BarBar, DM2 and BESIII Collaborations. We also predict the double spin polarization observables $A_{xx}$, $A_{yy}$ and $A_{zz}$ in $e^+e^-\rightarrow \bar\Lambda\Lambda$.