The $s\to d\gamma$ Transition in Kaon and Hyperon Decays

Abstract

We survey the possibilities of detecting the $s\to d\gamma$ transition in kaon and hyperon radiative decays. In the more frequent decays, like $K^{+}\to {\pi }^{+}{\pi }^o\gamma$, $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$, the short-distance contribution is obscured by various long-distance transitions. Among the hyperon radiative decays, ${\Xi }^{-}\to {\Sigma }^{-}\gamma$ and ${\Omega }^{-}\to {\Xi }^{-}\gamma$ are the leading candidates for providing a window to the short-distance $s\to d\gamma$. The long-distance $s\to d\gamma$ transitions are also analyzed; their magnitude depends on the size of the deviation from a sum-rule among couplings of vector mesons to photons. The measurement of ${\Omega }^{-}\to {\Xi }^{-}\gamma$ could provide information on the relative size of the short and long-distance contributions to the magnetic component of $s\to d\gamma$.

Lecture presented at the Workshop on K-Physics, Orsay, France, 30 May - 4 June, 1996. 9 pages