MEASUREMENT OF THE REACTIONS (P)OVER-BAR-P-](SIGMA(-BAR-SIGMA(+) AND (P)OVER-BAR-P-](SIGMA(-))OVER-BAR-SIGMA(-) CLOSE TO THRESHOLD())OVER)

The reactions (p) over bar p --> <(Sigma(+))over bar>Sigma(+) and (p) over bar p --> <(Sigma(-))over bar>Sigma(-) have been investigated at 1.922 GeV/c beam momentum by the PS185 Collaboration at LEAR, CERN. Of both reaction types together 170 events could be identified. The cros s section of the reaction (p) over bar p --> <(Sigma(+))over bar>Sigma (+) was determined to be sigma(tot) = 3.68 +/- 0.43 mu b at an excess energy of 23 MeV. Its angular distribution exhibits a pronounced forwa rd peaking. The ratio of the cross sections sigma((p) over bar p --> < (Sigma(+))over bar>Sigma(+))/sigma((p) over bar p --> <(Sigma(-))over bar>Sigma(-)) = 2.40(-1.3)(+3.0) was extracted with a confidence limit of 90%. It is the first time that experimental data of these reaction channels are available close to threshold. We compare our results wit h those of earlier experiments and with theoretical predictions. (C) 1 997 Elsevier Science B.V.