a Precision Measurement of the Magnetic Moment of the Sigma Minus Hyperon.

A new measurement of the magnetic moment of the (SIGMA)('-) hyperon has been made and the result is (mu)((SIGMA)(' -)) = -1.111 (+OR-) 0.031 (+OR-) 0.011 nuclear magnetons. Negative kaons from a low-energy separated beam at the Alternating Gradient Synchrotron of the Brookhaven National Laboratory were brought to rest in a novel laminar target consisting of thin metal foils immersed in liquid hydrogen. The production of (SIGMA)('-) hyperons occurred primarily through the reaction K('-)p(--->)(SIGMA)('-)(pi)('+). (SIGMA)(' -) hyperon production was tagged by the identification of the energetic (pi)('+). Many of the (SIGMA)('-) so produced stopped in nearby foils of Pb (or W) where atomic capture into a highly excited state could occur. The energies of the subsequent de-excitation x rays were recorded with three high-resolution intrinsic Ge detectors located below the target. The tagging technique resulted in an enhancement of 15 in x-ray signal-to-noise compared to that of previous (SIGMA)('-) exotic atom experiments. The (SIGMA)('-)Pb(11 -10), (SIGMA)('-)Pb(12-11), and (SIGMA)('-)W(11-10) transitions were analyzed for fine-structure from which the (SIGMA)(' -) magnetic moment was deduced. Self-consistent results were obtained from the three transitions and from the data accumulated in each detector.