Strong $\Lambda \pi$ Phase Shifts for CP Violation in Weak $\Xi   \rightarrow \Lambda \pi$ Decay
  Strong interaction $\Lambda\pi$ phase shifts relevant for the weak nonleptonic decay $\Xi \rightarrow \Lambda \pi$ are calculated using baryon chiral perturbation theory. We find in leading order that the S-wave phase shift vanishes and the $J={1 \over 2}$ P-wave phase shift is $-1.7 ^{\rm o} $. The small phase shifts imply that CP violation in this decay will be difficult to observe. Our results follow from chiral $SU(2)_L\times SU(2)_R$ symmetry. 
Ming Lu, Martin J. Savage and Mark B. Wise