Measurements of the magnetic dipole moments of the antiproton and theΣ−hyperon

Abstract

The fine-structure splittings in atoms formed by stopping antiprotons in Pb and U and ${\Sigma }^{-}$ hyperons in Pb and Pt have been measured. Since the fine structure is produced through the interaction of the magnetic dipole moment of the $\overline{p}$ or the ${\Sigma }^{-}$ with the Coulomb field of the nucleus, a value for the magnetic moment can be determined from the splitting. The magnetic moment obtained for the $\overline{p}$ was (-2.819 ± 0.056) nuclear magnetons, which agrees well with the $\mathrm{CPT}$ prediction of -2.793 nuclear magnetons. The magnetic moment derived for the ${\Sigma }^{-}$ was (-1.48 ± 0.37) nuclear magnetons, which is in agreement with the sign given by simple SU(3) theory, but differs somewhat from the value of -0.9 nuclear magnetons predicted by the theory with no mass breaking.