Higgs decay to a fermion pair
= Higgs decay to a fermion pair
{c}
{title2=$\Gamma(H\to f\bar f)$}
A scalar <Yukawa coupling> $-m_fH\bar f f/v$ gives
$$
\Gamma=\frac{N_cm_f^2m_H}{8\pi v^2}\left(1-\frac{4m_f^2}{m_H^2}\right)^{3/2}
$$
above threshold. The <fermion spin sum> provides the additional factor of momentum squared that turns the phase-space threshold factor into its third power. The <color multiplicity in a decay width> is $N_c=3$ for a quark pair and one for a lepton pair.