ΔI= 1/2 and epsilon′/epsilon in large-NcQCD

We present new results for the matrix elements of the Q_6 and Q_4 penguinoperators, evaluated in a large-Nc approach which incorporates importantO(N_c^2\frac{n_f}{N_c}) unfactorized contributions. Our approach shows analyticmatching between short- and long-distance scale dependences within dimensionalrenormalization schemes, such as MS-bar. Numerically, we find that there is alarge positive contribution to the Delta I =1/2 matrix element of Q_6 and henceto the direct CP-violation parameter epsilon'/epsilon. We also present resultsfor the Delta I = 1/2 rule in K -> pi pi amplitudes, which incorporate therelated and important ``eye-diagram'' contributions of O(N_c^2\frac{1}{N_c})from the Q_2 operator (i.e. the penguin-like contraction). The results lead toan enhancement of the Delta I = 1/2 effective coupling. The origin of the largeunfactorized contributions which we find is discussed in terms of the relevantscales of the problem.Comment: 25 pages, 8 figures, LaTeX file. Couple of references adde