Weak-decay channel counting
= Weak-decay channel counting
{title2=$\Gamma=C G_F^2m^5/(192\pi^3)$}
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.