LATTICE QCD CALCULATION OF THE K-]PI(+)PI(0) DECAY AMPLITUDE WITH THEWILSON QUARK ACTION()

We present our results for the K+ --> pi(+)pi(0) decay amplitude with the Wilson quark action in the quenched approximation at beta = 6.1. T he amplitude is extracted from the ratio of K --> pi pi 3-point functi on divided either by K and pi meson 2-point functions or by K meson a- point function and I = 2 pi pi 4-point function, which yield results i n good agreement. Finite size effects are examined with calculations m ade on 24(3) x 64 and 32(3) x 64 lattices. We convert the lattice ampl itude into the continuum value employing a recent one-loop calculation of chiral perturbation theory by Golterman and Leung. The result is c onsistent with the experimental value if extrapolated to the chiral li mit. Various uncertainties inherent in the present methods for calcula ting the decay amplitude are discussed.