Nonleptonic weak decays of mesons

A unified view for nonleptonic decays of mesons is presented on the basis of a model introduced for interpreting the enhancement of $D$- and $K$-meson decay. We show that inclusive and exclusive nonleptonic decays of mesons can be described in a unified picture and the enhancements in inclusive decays are closely related to two-body decays ($0^{-}$ $0^{-}$ decays). The model is applied to the decays of $K$, charmed, and $B$ mesons and predicts the values ${\left[\Gamma \right(K^{+}\to {\pi }^{+}{\pi }^0\left)\right]}^{-1\mathrm{}}\simeq 6.2\times {10}^{-8\mathrm{}}$ sec (expt. 5.9×${10}^{-8\mathrm{}}$ sec), $\frac{{\tau }^{+}}{{\tau }^0}\simeq 3-6$, $\frac{{\tau }^F}{{\tau }^0}\simeq 1.3-1.5$, $B(B^0\to e\nu X)\simeq 7-12\%$, $B(B^{-}\to e\nu X)\simeq \mathrm{}(10-12)\%$, where ${\tau }^0({\tau }^{+},{\tau }^F)$ is the lifetime of the $D^0(D^{+},F)$ meson and $B(A\to e\nu X)$ stands for the semileptonic branching ratio. The large difference between the ratios, $\frac{\Gamma (D^0\to {\overline{K}}^0{\pi }^0)}{\Gamma (D^0\to K^{-}{\pi }^{+})}\simeq {0.7}_{-0.4\mathrm{}}^{+0.7\mathrm{}}$ and $\frac{\Gamma (D^0\to {\overline{K}}^0{\rho }^0)}{\Gamma (D^0\to K^{-}{\rho }^{+})}\simeq {0.01}_{-0.01\mathrm{}}^{+0.10\mathrm{}}$, is naturally understood as the difference between the $s$-wave decays and the $p$-wave decays. We also point out that the model can include many of the models proposed up to this point, e.g., $W$-exchange model, quark-number-conservation model, penguin diagram, etc. We comment that the $\Delta I=\frac{1}{2}$ rule for hyperon decays is easily understood in the model.