Comparison ofΛandΣ0Production near Threshold in Proton-Proton Collisions

Threshold measurements of the associated strangeness production reactions $\mathrm{pp}\to {\mathrm{pK}}^{+}\Lambda$ and $\mathrm{pp}\to {\mathrm{pK}}^{+}{\Sigma }^0$ are presented. The most remarkable feature of the data is that at the same excess energy the total cross section for the ${\Sigma }^0$ production appears to be about a factor of ${28}_{-9\mathrm{}}^{+6\mathrm{}}$ smaller than for the $\Lambda$ particle. It is concluded that strong ${\Sigma }^{0}p$ final state interactions, and in particular the $\Sigma N\to \Lambda p$ conversion reaction, are the likely cause of the depletion in the $\Sigma$ signal. This hypothesis is in line with other experimental evidence in the literature.