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

Abstract

Abstract The electromagnetic form factors of the $$\Lambda $$ Λ 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 $$e^+e^-\rightarrow {\bar{\Lambda }}{\Lambda }$$ e + e - → Λ ¯ Λ . 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 $$\Lambda $$ Λ radius from chiral perturbation theory is taken as a constraint, the magnetic radius is predicted as $$r_M = 0.681 \pm 0.002$$ r M = 0.681 ± 0.002 fm. We also extract various vector meson to baryon coupling constants.