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

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