Polarization Effects inΣ−Capture

The interaction of very slow, or captured, polarized ${\Sigma }^{-}$ hyperons with protons, ${\Sigma }^{-}+p\to {\Lambda }^0+n$, may be used to yield information concerning the parity of $\Sigma$ relative to $\Lambda$, the ($\Sigma , \Lambda$) parity. A qualitative distinction between even and odd parity depends on whether or not the polarization of the emergent $\Lambda \text{'}\mathrm{s}$ varies with angle of emission. In order to determine the parity unambiguously it would furthermore be necessary to know whether the reaction proceeds from an initial $S$ or $P$ state. Aside from these questions, the polarization of the emergent $\Lambda \text{'}\mathrm{s}$ serves as a detector of the initial $\Sigma$ polarization. For example, if $\Sigma \text{'}\mathrm{s}$ produced under given circumstances do not show an appreciable up-down asymmetry in decay, the above reaction might help to decide whether this is due to negligible polarization of the ${\Sigma }^{-}$ in production.