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

Abstract

We survey the possibilities of detecting the $s \rightarrow d γ$ transition in kaon and hyperon radiative decays. In the more frequent decays, like $K^+ \rightarrow π^+ π^o γ$, $K^+ \rightarrow π^+ \ell^+ \ell^-$, the short-distance contribution is obscured by various long-distance transitions. Among the hyperon radiative decays, $Ξ^- \rightarrow Σ^- γ$ and $Ω^- \rightarrow Ξ^- γ$ are the leading candidates for providing a window to the short-distance $s \rightarrow d γ$. The long-distance $s \rightarrow d γ$ 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 $Ω^- \rightarrow Ξ^- γ$ could provide information on the relative size of the short and long-distance contributions to the magnetic component of $s \rightarrow d γ$.