I have seen vague explanations and (to me) misleading diagrams, and I am still not completely sure what is supposed to be happening in pion+/- decay. This Feynman diagram is a starting point. https://en.wikipedia.org/wiki/Pion#/media/File:PiPlus_muon_decay.svg What is happening? What happens to the quarks? I'm not asking for the unknowable, just a reasonable description of events and the fate of particles. Thank you.