Estimating epsilon'/epsilon in the Standard Model

TL;DR

This paper reviews theoretical estimates of epsilon'/epsilon within the Standard Model, emphasizing phenomenological methods like the chiral quark model to interpret experimental results amid limited first-principles calculations.

Contribution

It highlights the role of phenomenological approaches, especially the chiral quark model, in understanding epsilon'/epsilon and its relation to kaon decay dynamics.

Findings

Chiral quark model suggests enhancement of K -> pi pi matrix element of Q_6

Phenomenological approaches help interpret experimental epsilon'/epsilon data

Correlation between Delta I=1/2 rule and epsilon'/epsilon explained

Abstract

I discuss the comparison of the current theoretical calculations of epsilon'/epsilon with the experimental data. Lacking reliable ``first principle'' calculations, phenomenological approaches may help in understanding correlations among different contributions and available experimental data. In particular, in the chiral quark model approach the same dynamics which underlies the Delta I = 1/2 selection rule in kaon decays appears to enhance the K -> pi pi matrix element of the Q_6 gluonic penguin, thus driving epsilon'/epsilon in the range of the recent experimental measurements.