Exotic-atom measurement of the magnetic dipole moment of theΣ−hyperon

The magnetic dipole moment of the ${\Sigma }^{\mathrm{-}}$ hyperon has been determined from ${\Sigma }^{\mathrm{-}}$-atom x-ray transitions in natural lead and tungsten. Negative kaons were stopped in a target which consisted of sheets of W or Pb immersed in liquid hydrogen. The ${\Sigma }^{\mathrm{-}}$ resulting from the reaction $K^{\mathrm{-}}$p→${\Sigma }^{\mathrm{-}}$ ${\pi }^{+}$ were tagged by observing the monoenergetic ${\pi }^{+}$. X rays from ${\Sigma }^{\mathrm{-}}$ atoms were detected by intrinsic Ge detectors. The x-ray lines were analyzed for fine-structure splitting and the magnetic moment was determined from the measured splitting. The value obtained for the magnetic moment is μ(${\mathrm{\Sigma }}^{\mathrm{-}}$)=(-1.105±0.029±0.010)${\mathrm{\mu }}_{\mathit{N}}$ where the first error is statistical and the second systematic. This value is in reasonable agreement with measurements that used precession techniques and with the theoretical predictions of simple quark models.