Measurement of Decay Parameters for ${\Xi }^{-}\to \Lambda {\pi }^{-}$ Decay

Abstract

Based on 1.35 million polarized ${\Xi }^{-}$ events, we measure the parameter ${\varphi }_{\Xi }$ to be $-1.61^{\circ }\pm 2.66^{\circ }\pm 0.37^{\circ }$ for ${\Xi }^{-}\to \Lambda {\pi }^{-}$ decay. New results for the parameters ${\beta }_{\Xi }$ and ${\gamma }_{\Xi }$ are also presented. Assuming that the CP-violating phase-shift difference is negligible, we deduce the strong phase-shift difference between the P-wave and S-wave amplitudes of the $\Lambda \pi$ final state to be $3.17^{\circ }\pm 5.28^{\circ }\pm 0.73^{\circ }$. This strong phase-shift difference reduces the theoretical uncertainty in estimating the level of CP violation in $\Xi$-hyperon decay.

To be published in Physical Review Letters