Some Properties of ${\Xi }^{-}$ and ${\Xi }^0$ Hyperons Produced in $K^{-}p$ Interactions between 1.05 and 1.7 BeV/c

The production of cascade hyperons by incident $K^{-}$ on hydrogen has been studied from threshold (1.05 BeV/c) to 1.7 BeV/c. A sample of 1004 ${\Xi }^{-}$ and 206 ${\Xi }^0$ was obtained. Production cross sections rise over this momentum range, reaching about 150 μb for ${\Xi }^{-}{K}^{+}$ production and about 100 μb each for ${\Xi }^0{K}^0$ and $\Xi \pi K$. Production of the ${\Xi }^{*}\mathrm{}\left(1530\right)\mathrm{}$ near threshold is observed, and the assignment $I=\frac{1}{2}$ for this resonance is confirmed. The $\Xi$ decay analysis yields weak evidence for $J_{\Xi }=\frac{1}{2}$. For $J_{\Xi }=\frac{1}{2}$, our decay-parameter results are ${\alpha }_{{\Xi }^{-}}=-0.368\mathrm{}\pm 0.057$ and ${\Phi }_{{\Xi }^{-}}=invtan{\left(\frac{\beta }{\gamma }\right)}_{\Xi }=0.008\mathrm{}\pm 0.186$ rad. The final-state $\pi \Lambda$ phase difference is then $({\delta }_P-{\delta }_S)=invtan{\left(\frac{\beta }{\alpha }\right)}_{\Xi }=179\mathrm{}\pm 26$ deg. No significant violation of the $\Delta I=\frac{1}{2}$ rule was observed. The upper limit on the leptonic decay rate, $\frac{({\Xi }^{-}\to \Lambda e^{-}\overline{\nu })}{({\Xi }^{-}\to \Lambda {\pi }^{-})}$, was found to be 0.5%.