Precision Measurement of the Magnetic Moment of theΣ−Hyperon

The magnetic moment of the ${\Sigma }^{-}$ hyperon has been obtained from measurements of fine-structure splittings of x-ray transitions in ${\Sigma }^{-}$ exotic atoms. The use of targets consisting of sheets of Pb or W immersed in liquid hydrogen, and of a tagging technique utilizing the ${\pi }^{+}$ emitted in the reaction $K^{-}p\to {\Sigma }^{-}{\pi }^{+}$, resulted in improved x-ray signal-to-noise ratio by a factor of 15 over that in previous experiments. The present result is $\mu \left({\Sigma }^{-}\right)=(1.111\mathrm{}\pm 0.031\pm 0.011){\mu }_N$.