Measurement of the magnetic moment and of the decay parameters of the Ψ- hyperon

A measurement of the magnetic moment and of the decay parameters of the Ξ⁻ hyperon is reported. The measurement gave μ_Ξ=(-2.1±0.8) nuclear magnetons, corresponding to a gyromagnetic ratio of g_Ξ=4.2±1.6. The measured Ξ⁻ decay parameters are α_Ξ=-0.39±0.05, β_Ξ=0.08±0.26, γ_Ξ=0.92±0.03 (φ_Ξ=5°±16°); and the lifetime τ_Ξ=(1.637±0.050)×10⁻¹⁰ sec. In the accepted angular range for the production of the Ξ⁻ (about 4.2° K⁺+Ξ⁻, the polarization of the Ξ⁻ is 0.29 ± 0.10, 0.44 ± 0.09, 0.36 ± 0.10, and 0.21 ± 0.06 at laboratory momenta of 1.74, 1.80, 1.87, and 1.83 GeV/c, respectively.