π⁺ branching ratios into leptons:

In this example of a pion decay into leptons the conservation of angular momentum then determines the spin direction of the charged leptons, which have to be opposite to the (anti-)neutrino since pions do not carry spin. Finally, regarding conservation of momentum, the charged leptons have the same chirality as the neutrinos. The helicity of the neutrino must be ^-1. Hence, neutrino helicity determines the chirality of the charged lepton. Due to the fact that the probability to find a massive particle with unfavourable helicity goes with 1- b , the rate of the decay p ⁺->e⁺ n _e should be lower than for p ⁺->µ⁺ n _µ. With the approximation m_e²/m_p² <<1 the ratio of decay rates turns out to be

, where the first term describes the ratio of probabilities to generate a right-circular electron or muon, the second term represents the phase space difference. From the masses alone the p ⁺->e⁺ n _e decay would have been favoured by a factor of 5.5 (assuming scalar interaction)[Per87]. The experimental value is (1.267±0.023)*10^-4[PDG98] and thus confirms the validity of (V-A) interaction.