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

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.

Measurements of Σ+ and Σ− time-like electromagnetic form factors for center-of-mass energies from 2.3864 to 3.0200 GeV

“…The relative phase of the Λ EMFFs was extracted by fitting the angular distributions [21]. Many theoretical activities [30][31][32][33][34][35] arose after this measurement. In Ref.…”

$Λ\barΛ$ final-state interaction in the reactions $e^+e^-\to ϕΛ\bar Λ$ and $e^+e^- \to ηΛ\bar Λ$

“…Among those reactions, the one that received the by far strongest attention by theorists is e + e − → Λ Λ, since it allows one to determine the electromagnetic form factors of the Λ in the time-like region [26][27][28][29][30][31][32][33][34][35][36][37][38]. One-photon exchange can be expected to dominate, so that the reaction mechanism is practically known, and the partial waves of the final state are restricted to either 3 S 1 or 3 D 1 .…”