English

Are "Penguins" Black-and-White?

High Energy Physics - Phenomenology 2009-10-28 v1

Abstract

Contributions of low energy "eye" and "figure-eight" quark diagrams to the KπK \rightarrow \pi 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=12\Delta I = \frac{1}{2} (suppress the ΔI=32\Delta I = \frac{3}{2}) amplitudes naturally. The overall long-distance-induced enhancement of the ratio of the ΔI=12\Delta I = \frac{1}{2} amplitudes over the ΔI=32\Delta I = \frac{3}{2} amplitudes is estimated at around 4-8.

Keywords

Cite

@article{arxiv.hep-ph/9504227,
  title  = {Are "Penguins" Black-and-White?},
  author = {P. Zenczykowski},
  journal= {arXiv preprint arXiv:hep-ph/9504227},
  year   = {2009}
}

Comments

23 pages, LaTeX

R2 v1 2026-07-22T14:25:22.323Z