Weak-decay channel counting ($\Gamma =C{G}_F^2{m}^5/(192{\pi }^3)$)

In a massless Fermi interaction approximation, a charged-current decay channel contributes a common mass-to-the-fifth width multiplied by its mixing and final-state multiplicity factors. A final quark-antiquark pair has three color choices, while a lepton pair has one. An initial quark does not acquire a factor of three in its lifetime merely from its possible initial colors.