Strong Enhancement of $\epsilon'/\epsilon$ Through Final State Interactions

Abstract

We quantify the important effect of strong final state interactions in the weak $K\to2\pi$ amplitudes, using the measured $\pi$--$\pi$ phase shifts with J=0 and $I=0,2$. The final rescattering of the two pions provides a strong enhancement of the $\Delta I =1/2$ amplitude, which so far has been neglected in the theoretical predictions of $\epsilon'/\epsilon$. This correction increases the Standard Model prediction of $\epsilon'/\epsilon$ to values in good agreement with the experimental measurements.