English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

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

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

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