Based on 1.35 million polarized $\Xi^{ -}$ events, we measure the parameter $\phi_{ \Xi}$ 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.
Categories: hep-ex