Measurement of Sigma - production polarization and magnetic moment.

We have measured the production polarization of 265- and 310-GeV/c ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ in the inclusive reaction $p+\mathrm{Cu}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{\ensuremath{-}}+X$ using 400-GeV/c protons. The polarization was analyzed via the asymmetry in the weak decay ${\ensuremath{\Sigma}}^{\ensuremath{-}}\ensuremath{\rightarrow}n+{\ensuremath{\pi}}^{\ensuremath{-}}$, and has typical values of +0.20 with respect to the direction of the cross product of the incident-proton and ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ momenta. Using the spin-precession technique, we have determined the ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ magnetic moment to be -1.23\ifmmode\pm\else\textpm\fi{}0.03\ifmmode\pm\else\textpm\fi{}0.03 nuclear magnetons, where the statistical and systematic errors are shown separately.