I've been asked to find the ratio between the cross sections of the two folowing decais: Using the CKM matrix and the feynman diagrams for both decays, I reach the conclusion that the Ratio is exactly 1. However, consulting this document, http://pdg.lbl.gov/2012/tables/rpp2012-tab-baryons-Lambda.pdf We clearly see it is not. I do not understand where the problem lies. My reasoning is the following: - The decays are exactly the same, except for the final arrangement of the quarks - Since the vertices are the same, the probability of each interaction is the same in both cases. - Since the probabilities are the same, the interaction rates are the same. - Since the mass of the products is roughly equal in both cases, the density of final states is the same - The cross section is the same.