Polarization ofΣ+and Σ¯−hyperons produced by 800-GeV/cprotons

We have mesured the polarization of 375-GeV/c ${\mathrm{\Sigma }}^{+}$ and Σ¯ ${}_{}{}^{\mathrm{-}}{}_{}{}^{}$ hyperons produced by 800-GeV/c protons incident on a Cu target. We find that the ${\mathrm{\Sigma }}^{+}$ polarization rises with increasing ${\mathit{p}}_{\mathit{t}}$ to a maximum of 16% at ${\mathit{p}}_{\mathit{t}}$=1.0 GeV/c and then decreases to 10% at ${\mathit{p}}_{\mathit{t}}$=1.8 GeV/c. We compare this ${\mathrm{\Sigma }}^{+}$ polarization with data at lower energies. The Σ¯ ${}_{}{}^{\mathrm{-}}{}_{}{}^{}$ polarization has been measured for the first time. It has the same sign as the ${\mathrm{\Sigma }}^{+}$ but smaller magnitude in a similar kinematical region.