Extended analysis of the "penguin" part of Ktoππ amplitude

We make an attempt to clarify the role of the annihilation or "penguin" mode in the description of the $K\rightarrow\pi\pi$ decay within the Standard Model. The attention is concentrated on new operators in the effective $\Delta S=1$ Hamiltonian and the violation of factorization for mesonic matrix elements of the local four-quark operators. We propose a regular method to evaluate the mesonic matrix elements of $K\rightarrow\pi\pi$ transitions based on studying three-point correlators via {\it QCD} sum rules using the chiral effective theory as an underlying low-energy model for strong interaction. Matrix elements of the {\it QCD} penguin operator are calculated within this approach. The total "penguin" contribution is found to be relatively large that improves the theoretical description of the $\Delta I=1/2$ rule in non-leptonic kaon decays.