1. Consider the competing reations
One might suspect that the decay via the positron would dominate. However the opposite is true. The reason for this involve angular momentum conservation and the chiral nature of the weak interaction.
In the limit of zero mass the states of definite chirality are states of definite helicity. Discuss the connection between the helicty states and the chiral states.
Use the above discussion to explain the branching ratios for muon and positron decay channels.
2. The neutral kaon decays into pions.
a. Define the kaon states that are useful and explain why they are used.
b. Explain what happens under C and P.
c. Under what conditions would CP be conserved?