Experimental Determination of theKΣNParity Using a Polarized Target

Abstract

We have determined the $K\Sigma N$ parity using the reaction ${\pi }^{+}p\to K^{+}{\Sigma }^{+}$. A crystal containing polarized protons was used as the target. We have compared the counting rates for events produced from protons polarized parallel and antiparallel to ${\mathrm{P}}_{\Sigma }$, where ${\mathrm{P}}_{\Sigma }$ is the polarization of $\Sigma \text{'}\mathrm{s}$ produced from unpolarized protons and has been previously measured. A higher counting rate was obtained for events for which the protons were polarized parallel to ${\mathrm{P}}_{\Sigma }$. This means that the $K\Sigma N$ parity ${\Pi }_{K\Sigma N}={\Pi }_{\pi p}=-1\mathrm{}$. This result depends only on the assumptions of spin ½ for the $\Sigma$ and parity conservation in the reaction. The relative probability of odd-versus-even $K\Sigma N$ parity is 21:1. Our result agrees with the usual expectations (as from $S{U}_3$) and with a previous experimental determination.