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arXiv · hep-ph/9504227

Are "Penguins" Black-and-White?

P. Zenczykowski
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Abstract

Contributions of low energy "eye" and "figure-eight" quark diagrams to the $K \rightarrow π$ weak transitions are studied in a hadron- level phenomenological approach. It is shown that these contributions may be estimated by considering meson-cloud effects. If all intermediate mesons under consideration are degenerate only the "eye" (low-energy penguin) diagram is nonvanishing. When allowance is made for smaller mass of pseudoscalar mesons, the contribution of "figure-eight" diagrams turns out to enhance the $ΔI = \frac{1}{2}$ (suppress the $ΔI = \frac{3}{2}$) amplitudes naturally. The overall long-distance-induced enhancement of the ratio of the $ΔI = \frac{1}{2}$ amplitudes over the $ΔI = \frac{3}{2}$ amplitudes is estimated at around 4-8.

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P. Zenczykowski. 1995-04-05. Are "Penguins" Black-and-White?. https://doi.org/10.1103/physrevd.54.907

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