Near threshold Λ and Σ production in pp collisions


A model calculation for the reactions pp → pΛK + and pp → NΣK near their thresholds is presented. It is argued that the experimentally observed strong suppression of Σ 0 production compared to Λ production at the same excess energy could be due to a destructive interference between the π and K exchange contributions in the reaction pp → pΣ 0 K +. Predictions for pp → pΣ + K 0 and pp → nΣ + K + are given. In a recent measurement of the reactions pp → pΛK + and pp → pΣ 0 K + near their thresholds it was found that the cross section for Σ 0 production is about a factor of 30 smaller than the one for Λ production [1]. We want to report on an exploratory investigation of the origin of this strong suppression of the near-threshold Σ 0 production [2]. In particular we want to examine a possible explanation that was suggested in Ref. [1], namely effects from the strong ΣN final state interaction (FSI) leading to a ΣN → ΛN conversion. We treat the associated strangeness production in the standard distorted wave Born approximation. We assume that the strangeness production process is governed by the π- and K exchange mechanisms. In order to have a solid basis for our study of possible conversion effects we employ a microscopic Y N interaction model developed by the Jülic

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