Paper detail

Analysis of ε'/εin the 1/N_c Expansion

We present a new analysis of the ratio ε'/εwhich measures the direct CP violation in K\toππdecays. We use the 1/N_c expansion within the framework of the effective chiral lagrangian for pseudoscalar mesons. The 1/N_c corrections to the hadronic matrix elements of all operators are calculated at leading order in the chiral expansion. Numerically, doing a simple scanning of the input parameters we find 1.5 \cdot 10^{-4}\leq ε'/ε\leq 31.6\cdot 10^{-4}. We also investigate, in the chiral limit, the 1/N_c corrections to the operator Q_6 at next-to-leading order in the chiral expansion. We find large positive corrections which can further enhance ε'/εand bring the standard model prediction close to the measured value for central values of the parameters. Our result indicates that a ΔI=1/2 enhancement may be operative for Q_6 similar to the one of Q_1 and Q_2 which dominate the CP conserving amplitude.