Properties of theΞ−and theΞ*(1817)fromK−pInteractions above 1.7 BeV/c

A sample of 2529 ${\Xi }^{-}$ hyperons, produced in ${\Xi }^{-}{K}^{+}$, ${\Xi }^{-}{K}^{+,0\mathrm{}}{\pi }^{0,+}$, and ${\Xi }^{-}{K}^{+,0\mathrm{}}{\pi }^{-,0\mathrm{}}{\pi }^{+}$ final states by $K^{-}$ (in hydrogen) at incident momenta from 1.7 to 2.7 BeV/c, has been analyzed. The data are from an exposure of 26 events/μb ("$K-63\mathrm{}$" run) in the Alvarez 72-in. bubble chamber; approximately 85% of the ${\Xi }^{-}$ events with visible $\Lambda$ decay have been analyzed. A maximum-likelihood fit (with ${\alpha }_{\Lambda }=0.656\mathrm{}\pm 0.055$ and with the $\Xi \mathrm{spin}=\frac{1}{2}$) yields the following values of ${\Xi }^{-}$ decay parameters: ${\alpha }_{{\Xi }^{-}}=-0.375\mathrm{}\pm 0.051$; ${\Phi }_{{\Xi }^{-}}\equiv invtan\left(\frac{{\beta }_{{\Xi }^{-}}}{{\gamma }_{{\Xi }^{-}}}\right)=9.8\mathrm{}°\pm 11.6°$. Spin analysis of the 3278 ${\Xi }^{-}$ decays from the $K-63\mathrm{}$ and $K-72\mathrm{}$ ($K^{-}p$ at 1.2-1.7 BeV/c) experiments gives likelihood results which favor $J_{\Xi }=\frac{1}{2}$ over $J_{\Xi }=\frac{3}{2}$ by the equivalent of approximately 2.5 standard deviations. Analysis of the ${\Xi }^{*}\mathrm{}\left(1817\right)\mathrm{}\to {\Xi }^{*}\mathrm{}\left(1530\right)+\pi$ decay mode indicates that the hypotheses $J^P={\frac{1}{2}}^{+}, {\frac{1}{2}}^{-}, {\frac{3}{2}}^{-}, {\frac{5}{2}}^{+}, {\frac{7}{2}}^{-}$, etc. are favored; but results are inconclusive because of high background as well as poor statistics. Analysis of the ${\Xi }^{*}\mathrm{}\left(1817\right)\mathrm{}\to \Lambda +\overline{K}$ provides no spin or parity discrimination. The $K-63\mathrm{}$ beam channel is briefly bescribed.