## Abstract

Dispersive effects from strong ππ rescattering in the final state interaction (FSI) of weak K→ ππ decays are revisited with the goal to have a global view on their relative importance for the Δ I= 1 / 2 rule and the ratio ε^{′}/ ε in the standard model (SM). We point out that this goal cannot be reached within a pure effective (meson) field approach like chiral perturbation theory in which the dominant current–current operators governing the Δ I= 1 / 2 rule and the dominant density–density (four-quark) operators governing ε^{′}/ ε cannot be disentangled from each other. But in the context of a dual QCD approach, which includes both long-distance dynamics and the UV completion, that is, QCD at short-distance scales, such a distinction is possible. We find then that beyond the strict large N limit, N being the number of colours, FSIs are likely to be important for the Δ I= 1 / 2 rule but much less relevant for ε^{′}/ ε. The latter finding diminishes significantly hopes that improved calculations of ε^{′}/ ε would bring its SM prediction to agree with the experimental data, opening thereby an arena for important new physics contributions to this ratio.

Originalsprache | Englisch |
---|---|

Aufsatznummer | 10 |

Fachzeitschrift | European Physical Journal C |

Jahrgang | 77 |

Ausgabenummer | 1 |

DOIs | |

Publikationsstatus | Veröffentlicht - 1 Jan. 2017 |

## Fingerprint

Untersuchen Sie die Forschungsthemen von „Final state interactions in K→ ππ decays: Δ I= 1 / 2 rule vs. ε^{′}/ ε“. Zusammen bilden sie einen einzigartigen Fingerprint.