Polarization ofΣ−in the Reactionπ−+p→Σ−+K+at 1130MeVc

We have measured the polarization $P_{{\Sigma }^{-}}$ of the ${\Sigma }^{-}$ in the production reaction ${\pi }^{-}+p\to {\Sigma }^{-}+K^{+}$ due to a ${\pi }^{-}$ beam of momentum 1130 $\frac{\mathrm{MeV}}{c}$ striking a polarized proton target. We find $P_{{\Sigma }^{-}}$ to lie between -0.1 and -0.5 in each of seven angular bins in the range $-1.0<cos{{\theta }_{\Sigma }}^{*}<0.3\mathrm{}$. Combining this and other measurements, we have performed an energy-dependent partial-wave analysis of the associated production reactions $\pi p\to \Sigma K$ between threshold and 1170 $\frac{\mathrm{MeV}}{c}$, using only $S$ and $P$ waves below 1130 $\frac{\mathrm{MeV}}{c}$ but including $D$ waves at higher momenta. Using a momentum-dependent form for the amplitudes first proposed by Lee et al., we find the $I=\frac{3}{2}$ amplitudes to be uniquely determined over the whole energy range, but the $I=\frac{1}{2}$ amplitudes to have several solutions of similar, but low, likelihood. Thus, this particular parametrization does not appear to hold for the $I=\frac{1}{2}$ channels near threshold. A possible reason is the presence of a highly inelastic $P_{11}$ resonance in the direct channel.