KAON-NUCLEON COUPLINGS FOR WEAK DECAYS OF HYPERNUCLEI

We investigate the weak kaon-nucleon (NNK) S-wave and P-wave interacti ons using heavy baryon chiral perturbation theory. The leading one-loo p SU(3) breaking contributions to the ppK, pnK, and nnK couplings are computed. We find that they suppress all NNK amplitudes by 30% to 50%. The ratio of neutron-induced to proton-induced hypernuclear decay wid ths is sensitive to such reductions. It has been argued that the discr epancy between the predicted and observed P-wave amplitudes in Delta s =1 hyperon decay results from an accidental cancellation between tree- level amplitudes, and is not a fundamental problem for chiral perturba tion theory. Agreement between experimentally determined NNK P-wave am plitudes and our estimates would support this explanation.