Hyperon electromagnetic form factors in the timelike region

Electromagnetic form factors of hyperons (Lambda, Sigma, Xi) in the timelike region, accessible in the reaction e(+)e(-) -> (Y) over barY, 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 (Y) over barY system. This interaction is taken into account in the calculation, utilizing (Y) over barY potential models that have been constructed by the Julich group for the analysis of data from the reaction (p) over barp -> (Y) over barY in the past. The enhancement of the effective form factor for energies close to the threshold, seen in experiments of e(+)e(- )-> (Lambda) over bar Lambda and e(+)e(-) -> (Sigma) over bar (0)Lambda, is reproduced. With regard to the reactions e(+)e(-) -> (Sigma) over bar (-)Sigma(+), (Sigma) over bar (0)Sigma(0), (Sigma) over bar+Sigma(-) a delicate interplay between the three channels is observed in the results at low energies, caused by the (Sigma) over bar Sigma interaction. Predictions for the electromagnetic form factors G(M) and G(E) in the timelike region are presented for the Lambda, Sigma, and Xi hyperons.