A short look at epsilon'/epsilon

Abstract

We analyze the theoretical implications of the new KTeV measurement of direct CP-violation in K->pi pi decays. The result is found consistent with the Standard Model for low values of the strange quark mass m_s. If the hadronic parameters B_6^{(1/2)} and B_8^{(3/2)} satisfy 2 B_6^{(1/2)} - B_8^{(3/2)} < 2, as suggested by lattice and 1/N_c calculations, we find an upper bound of 110 MeV for m_s (2 GeV)$. We parametrize potential new physics contributions to \epsilon'/\epsilon and illustrate their correlation with upper bounds on m_s. Finally we discuss a non-perturbative mechanism, which is not contained in the existing calculations of B_6^{(1/2)}. This mechanism enhances B_6^{(1/2)} and thereby leads to a better understanding of the Delta I=1/2 rule and the high measured value of Re (\epsilon^\prime/\epsilon)

Comments: typo in eq. (5) corrected, 2 refs. added, some clarifications in text, keywords/PACS-no. added