Measurement of the ${\Sigma }^{-}$ Magnetic Moment Using the ${\Sigma }^{-}\to n{e}^{-}\overline{\nu }$ and ${\Sigma }^{-}\to n{\pi }^{-}$ Decay Modes

We have used the spin-precession technique to measure the ${\Sigma }^{-}$ magnetic moment (${\mu }_{\Sigma }$). A ${\Sigma }^{-}$ beam with a polarization of 22% was produced by a 400-GeV proton beam striking a Cu target at nominal production angles of ±3 mrad. We simultaneously recorded 21 000 ${\Sigma }^{-}\to n{e}^{-}\overline{\nu }$ decays and 650 000 ${\Sigma }^{-}\to n{\pi }^{-}$ decays at ${\Sigma }^{-}$ beam momenta of 253 and 308 GeV/c. We find ${\mu }_{\Sigma }=-1.166\mathrm{}\pm 0.014\pm 0.010$ nuclear magnetons, where the quoted errors are statistical and systematic, respectively.