Upper Limits on Cross Sections forγ+n→K0+Λ0(Σ0)below 1500 MeV

Abstract

A search for the reactions $\gamma +n\to K^0+\Lambda$ and $\gamma +n\to K^0+{\Sigma }^0$ has been conducted using the Cal Tech heavy-liquid bubble chamber as the detector with a central internal target. Photon energies were from threshold to 1530 MeV. The absence of any real events in 14 000 pictures implies a joint upper limit on the average total cross sections ${\overline{\sigma }}_{\Lambda }$ and ${\overline{\sigma }}_{\Sigma }$ in this energy region. If the ratio $\frac{{\overline{\sigma }}_{\Lambda }}{{\overline{\sigma }}_{\Sigma }}$ is near unity, we find at the 90% confidence level: ${\overline{\sigma }}_{\Lambda }\le 2.4$ μb, ${\overline{\sigma }}_{\Sigma }\le 2.1$ μb.