The reactions pp → pΛK+ and pp → pΣ0K+ near their thresholds

The reactions pp --> p Lambda K+ and pp --> p Sigma(0)K(+) are studied near their thresholds. The strangeness production process is described by the pi- and K exchange mechanisms. Effects from the final stare interaction in the hyperon-nucleon system are taken into account rigorously. The Lambda production turns out to be dominated by K exchange whereas K- as well as pi exchange play an important role for the Sigma(0) case. It is shown that the experimentally observed strong suppression of Sigma(0) production compared to ii production at the same excess energy can be explained by a destructive interference between rr and K exchange in the reaction pp --> p Sigma(0) K+ Implications of such an interference on the reaction pp --> n Sigma(+)K(+) are pointed out. (C) 2000 Elsevier Science B.V. All rights reserved.