New measurements of properties of theΩ−hyperon

We have obtained a sample of 1743 reconstructed ${\Omega }^{\mathrm{-}}$→Λ$K^{\mathrm{-}}$ events produced by protons on a Be target at production angles of 5.0 and 7.5 mrad. The ${\Omega }^{\mathrm{-}}$ lifetime, based on a subset of 1096 events, was measured to be τ(${\mathrm{\Omega }}^{\mathrm{-}}$)=(0.811±0.037)×${10}^{\mathrm{-}10}$ sec, where the uncertainty is statistical and the systematic uncertainty is estimated to be small. The helicity of the daughter Λ yielded the product of asymmtery parameters ${\alpha }_{\Lambda }$ ${\alpha }_{\Omega }$=-0.022±0.051 which, in turn, yields ${\alpha }_{\Omega }$=-0.034±0.079. The average daughter-Λ polarization in the decay region was measured to be $P_{\Lambda }$=0.12±0.08 approximately perpendicular to the charged-hyperon beam line. The ${\Omega }^{\mathrm{-}}$ polarization in the same region, i.e., after the precession magnet, depends on the sign of ${\gamma }_{\Omega }$, which is unknown at present. The two possibilities are $P_{\Omega }$=$P_{\Lambda }$ if ${\gamma }_{\Omega }$≊+1 and $P_{\Omega }$=-(5/3$P_{\Lambda }$ if ${\gamma }_{\Omega }$≊-1. The magnitude of the polarization vector is only 1.5 standard deviations different from zero, and this prevented a meaningful measurement of the ${\Omega }^{\mathrm{-}}$ magnetic moment. If the broken-SU(6) prediction for the moment, μ(${\Omega }^{\mathrm{-}}$)=-1.83${\mu }_N$, is assumed to be true, then the precession of the ${\Omega }^{\mathrm{-}}$ in the magnetic field is small and the values of $P_{\Omega }$ above are also true at the production target. If this polarization is different from zero and correct in sign, then it cannot be simultaneously reconciled with theoretical predictions for the sign of ${\gamma }_{\Omega }$ and for the sign of the production polarization. On the other hand, if the polarization is zero no inconsistency exists.