Question

write selection rules for semi-leptonic and non-leptonic weak decays.discuss in detail by using examples and Feynman diagram

Answer 1

Selection rule for semi-leptonic weak decay:

$$K^-\rightarrow\mu^-+\bar{\nu_\mu}+\pi^0.$$

The final state consists of a lepton pair.

$$\Delta S=\Delta Q=Q_\text{final}-Q_\text{initial}=+1.$$

Selection rule for non-leptonic weak decay:

$$K^-\rightarrow\pi^0+\pi^-,\\ \Delta I=1/2.$$