Mass and magnetic moment of Σ − by the exotic atom method

Abstract

The energies and lineshapes of five circular transitions ( n = 15 → n = 14 through n = 11 → = 10) of the Σ −Pb atom were measured wit of the transitions 15 → 14 through 12 → 11 were determined; these energies were compared with energies calculated from quantum electrodynamics, and the mass of Σ − was adjusted to achieve a best fit. The result was m Σ − = 1197.24 ±0.15 MeV. The lineshape of the 12→11 transition, which is broadened by the fine structure, has been analyzed to extract the magnetic moment of Σ −. The result was μ Σ − = −1.40 −0.28 +0.41or 0.651 −0.40 +0.28 nuclear magnetons. Comparisons with SU (3) predictions are made.