Hi, Given the initial energy of a pion is it possible to calculate the probability and mode of its decay? Ive looked everywhere for a relevent formula but everywhere simply states the probability and mode.... Wiki "The primary decay mode of a pion, with probability 0.999877, is a purely leptonic decay into an anti-muon and a muon neutrino"... "The second most common decay mode of a pion, with probability 0.000123, is also a leptonic decay into an electron and the corresponding electron antineutrino." I considered doing some sort of conservation of energy / momentum, but how am i supposed to do that if i dont know what it decays into? ive spent at least two hours trying to find an equation, i found something called the "branching ratio" is that at all related? any direction on this would be appreciated.