Dispersion-theoretical analysis of the electromagnetic form factors of the $\Lambda$ hyperon

TL;DR

This paper performs a dispersion-theoretical analysis of the electromagnetic form factors of the Lambda hyperon in the time-like region, providing precise parameterizations and insights into their properties and related couplings.

Contribution

It introduces a novel dispersion-theoretical approach to analyze Lambda hyperon form factors using world data and tests different spectral function scenarios.

Findings

Good description of time-like data achieved

Magnetic radius predicted as 0.681 ± 0.002 fm

Vector meson to baryon coupling constants extracted

Abstract

The electromagnetic form factors of the $\Lambda$ hyperon in the time-like region are determined precisely through a dispersion-theoretical analysis of the world data for the cross section of the annihilation process $e^+e^-\to \bar{\Lambda}{\Lambda}$. The spectral function is represented by a superposition of narrow and broad vector meson poles. We test different scenarios for the spectral function and obtain a good description of the world data in the time-like region. The uncertainties in the extracted form factors are estimated by means of the bootstrap sampling method. The analytical continuation of the form factors to the space-like region introduces large errors due to the lack of data. When the electric $\Lambda$ radius from chiral perturbation theory is taken as a constraint, the magnetic radius is predicted as $r_M = 0.681 \pm 0.002$ fm. We also extract various vector meson to baryon coupling constants.