Light quark loops in $K^\pm \to \pi^\pm \nu\bar\nu$ from vector meson dominance and update on the Kaon Unitarity Triangle

TL;DR

This paper calculates non-perturbative effects of light quark loops in rare kaon decays using vector meson dominance and updates the Kaon Unitarity Triangle analysis based on these observables.

Contribution

It introduces a vector meson dominance approach to evaluate non-perturbative contributions in rare kaon decay processes and updates the Kaon Unitarity Triangle analysis accordingly.

Findings

Quantifies non-perturbative contributions to $K^ ightarrow uar u$ decay

Highlights the significance of kaon decay observables in CKM unitarity tests

Provides an updated analysis of the Kaon Unitarity Triangle

Abstract

We use vector meson dominance to calculate non-perturbative contributions to the branching ratio of the rare decay $K^\pm \to \pi^\pm \nu\bar \nu$ stemming from matrix elements involving up-quark loops. The importance of this observable as well as of $K^0 \to \pi^0 l^+ l^-$ and of the direct CP violation parameter $\epsilon_K^{\prime}$ is then discussed in the context of a Unitarity Triangle sqtudy based on Kaon sector observables only.