Meson exchange in the weak decay of Λ hypernuclei and the Γn/Γp ratio Original Research Article

We take an approach to the Λ nonmesonic weak decay in nuclei based on the exchange of mesons. The one-pion and one-kaon exchange are considered, together with the exchange of two pions, either correlated, leading to an important scalar–isoscalar exchange (σ-like exchange), or uncorrelated (box diagrams). Extra effects of ω exchange in the scalar–isoscalar channel are also considered. Constraints of chiral dynamics are used to generate these exchanges. A drastic reduction of the OPE results for the Γn/Γp ratio is obtained and the new results are compatible with all present experiments within errors. The absolute rates obtained for different nuclei are also in good agreement with experiment.