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.

 

  1. Define what is meant by chirality.
  2. Use helicity to describe the final state angular momentum.
    1. Define helicty
    2. Draw a diagram to show possible final states.

 

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?