K-] 2-PI AND K-] 3-PI DECAYS IN NEXT-TO-LEADING ORDER CHIRAL PERTURBATION-THEORY

We evaluate the next-to-leading corrections to K --> 2-pi and K --> 3-pi decays in chiral perturbation theory. Fitting the counterterm coupling constants of the next-to-leading order corrections to isospin amplitudes determined from the decay rates and slope parameters, we conclude that the lowest-order value of the octet coupling constant is reduced by about 30% while the 27-plet coupling constant remains unchanged. With the exception of one slope parameter, the amplitudes evidence no breakdown of chiral perturbation theory. As an additional result, the determination of the isospin amplitudes predicts that the branching ratio for K(s) --> pi+ pi- pi-0 be (2.4 +/- 0.7) x 10(-7).