High-statistics measurement of polarization inπ−p→K0Λat 3 and 5 GeV/c

We have measured the polarization of the $\Lambda$ hyperon produced in the reaction ${\pi }^{-}p\to K^0\Lambda$ at 3 and 5 GeV/c, for four-momentum transfers $t^{\prime }$ out to 1.6 ${\mathrm{GeV}}^2$, by observing the parity-violating decay $\Lambda \to p{\pi }^{-}$. With an increase in statistical power by a factor of 3 to 4 over the best previous experiments in this energy range, we confirm earlier observations that the polarization is small and positive below $t^{\prime }=0.4\mathrm{}$ ${\mathrm{GeV}}^2$, becoming large and positive for larger values of $t^{\prime }$. In particular, at 5 GeV/c for all $t^{\prime }$ between 0.8 and 1.6 ${\mathrm{GeV}}^2$ the polarization is consistent with a value of - 1.