W boson decay to a quark pair
= W boson decay to a quark pair
{c}
{title2=$\Gamma(W^+\to q\bar q\prime)$}
Ignoring accessible quark masses and strong corrections, the <W boson> flavor width is $\Gamma(W^+\to q\bar q')=N_cG_FM_W^3|V_{qq'}|^2/(6\pi\sqrt2)$. The <CKM matrix> fixes the flavor factor, while the <color multiplicity in a decay width> supplies $N_c=3$. Only the up and charm rows are accessible for an on-shell <W boson>, giving a total hadronic width $G_FM_W^3/(\pi\sqrt2)$ by row unitarity.