Hyperon electromagnetic form factors in the timelike region

Electromagnetic form factors of hyperons ($\mathrm{\Lambda }$, $\mathrm{\Sigma }$, $\mathrm{\Xi }$) in the timelike region, accessible in the reaction $e^{+}{e}^{-}\to \bar{Y}Y$, are studied. The focus is on energies close to the reaction thresholds, where the properties of these form factors are significantly influenced by the interaction in the final $\bar{Y}Y$ system. This interaction is taken into account in the calculation, utilizing $\bar{Y}Y$ potential models that have been constructed by the J"ulich group for the analysis of data from the reaction $\bar pp \to \bar YY$ in the past. The enhancement of the effective form factor for energies close to the threshold, seen in experiments of $e^+e^- \to \bar \Lambda \Lambda$and$e^+e^- \to \bar \Sigma^0\Lambda$, is reproduced. With regard to the reactions $e^+e^- \to \bar \Sigma^- \Sigma^+, \ \bar\Sigma^0\Sigma^0,
\bar\Sigma^+\Sigma^-$ a delicate interplay between the three channels is observed in the results at low energies, caused by the $\bar{\mathrm{\Sigma }}\mathrm{\Sigma }$ interaction. Predictions for the electromagnetic form factors $G_M$ and $G_E$ in the timelike region are presented for the $\mathrm{\Lambda }$, $\mathrm{\Sigma }$, and $\mathrm{\Xi }$ hyperons.