DispersiveKL→μ+μ−contributions, neutral-kaon mixing, and mass of the top quark

Abstract

We estimate the $K_L\to 2\mu$ weak amplitude from data, by relating the dispersive $K_L\to 2\gamma \to 2\mu$ amplitude to that of $\eta \to 2\mu$. Allowed bands of mixing angles ${\theta }_2$,${\theta }_3$ are determined from this weak amplitude. The bands overlap those from analyses of $K^0-{\overline{K}}^0$ mixing, with rather loose constraints on the $t$-quark mass which depend sensitively on the bag factor $B$. For $B=0.4\mathrm{}$, $m_t$ is likely to be less than 75 GeV.