The reactions $pp\to pΛK^+$ and $pp\to pΣ^0K^+$ near their thresholds

Abstract

The reactions $pp\to pΛK^+$ and $pp\to pΣ^0K^+$ are studied near their thresholds. The strangeness production process is described by the $π$- and $K$ exchange mechanisms. Effects from the final state interaction in the hyperon-nucleon system are taken into account rigorously. It is found that the $Λ$ production is dominated by $K$ exchange whereas $K$- as well as $π$ exchange play an important role for the $Σ^0$ case. It is shown that the experimentally observed strong suppression of $Σ^0$ production compared to $Λ$ production at the same excess energy can be explained by a destructive interference between $π$ and $K$ exchange in the reaction $pp\to pΣ^0K^+$. Implications of such an interference on the reaction $pp\to nΣ^+K^+$ are pointed out.

Revised version with corrected numerical results. The general conclusions remain unchanged