Light quark loops in $K^{\pm }\to {\pi }^{\pm }\nu \bar{\nu }$ from vector meson dominance and update on 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.

22 pages, 5 figures