$K^{+}\to {\pi }^{+}{\pi }^0$ Decay Amplitude in Quenched Lattice QCD

A new study is reported of a lattice QCD calculation of the $K^+\to\pi^+ \pi^0 $ decay amplitude with the Wilson quark action in the quenched approximation at $\beta =6.1$. The amplitude is extracted from the $K\to \pi \pi$ Green function, and a conversion to the continuum value is made employing a recent one-loop calculation of chiral perturbation theory. The result is consistent with the experimental value if extrapolated to the chiral limit.