My background of some introductory courses in particle physics has left me with severe shortcomings. Say we start from a hadron, which decays purely to other hadrons. My question is this: through which interaction does the process take place? Is there a preferred interaction, and why/why not? Let me put my thoughts/guesses/current understanding here. A process in which the flavour of one or more quarks in the original hadron changes, must happen through weak interaction, and there are no other options. Processes in which the flavours don't change could happen either through strong, weak or electromagnetic interaction. Right? Now, my guess is that there is a preference. How should I see this exactly? I thought about comparing the coupling constants, but I've understood that the coupling constant of the strong force depends on the distance of the quarks. Then again, how far can I get the quarks from each other depends on the energy they have. So once I fix the energy scale, I would be able to compare the couplings? Or is there an easier approach? Or am I missing something?