A short look at epsilon'/epsilon

TL;DR

This paper examines the implications of recent measurements of direct CP-violation in kaon decays, exploring Standard Model consistency, potential new physics, and non-perturbative effects influencing key parameters.

Contribution

It provides a detailed analysis of the theoretical implications of new experimental data, proposing bounds on the strange quark mass and exploring mechanisms affecting hadronic parameters.

Findings

Consistency of measurements with the Standard Model for low m_s

Upper bound of 110 MeV on m_s (2 GeV) under certain conditions

Identification of a non-perturbative mechanism enhancing B_6^{(1/2)}

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)