Nonleptonic meson decay

A nonleptonic meson decay contains final hadrons and no final leptons. Weak quark transitions set flavour factors, but strong hadronization and additional hadronic matrix elements are needed to determine exclusive rates.

For Ds meson spectator decays, $c\to s{W}^{+}$ followed by $W^{+}\to u\bar{d}$ carries CKM magnitude $|V_{cs}{V}_{ud}|$ and can form either $\varphi {\pi }^{+}$ or $K^{+}{\bar{K}}^0$. Replacing $c\to s$ by $c\to d$ carries $|V_{cd}{V}_{ud}|$ and can form $K^{+}{\pi }^0$ through the $-d\bar{d}/\sqrt{2}$ pion component. With otherwise equal reduced hadronic strengths, the last channel's rate is suppressed relative to the neutral-antikaon channel by $|V_{cd}/V_{cs}{|}^2/2$. Actual branching fractions also depend on phase space, colour contractions and strong final-state interactions; the CKM factors do not determine exact exclusive rates.