Class #1 (Jan. 17) Reading Questions - Particle Physics, Sec. 4; Handout pgs. 59-66

1. The Dirac equation, the relativistic wave equation for spin 1/2 particles, involves a 4-component wave-function (usually represented as a column vector). What is the physical interpretation of the four components?

2. According to the handout how do you distinguish a particle from an antiparticle in a Feynman diagram? Based on the handout, what is wrong with the QED diagrams shown in Figs. 4.3 and 4.4 of our text. [By the way, correctly drawn Feynman diagrams provide a visual representation of the Feynman-Stuckelberg interpretation of Dirac's "sea of negative energy particles".]

3. What is a "virtual" particle? How do you distinguish real particles from "virtual" particles in a Feynman diagram?

4. Why does one typically not bother calculating QED Feynman diagrams with more than say 4 vertices?

5. What is meant by renormalization? People often talk about the "bare electron mass". What do you think this means?

Your Question: Please give a well formulated question that you have regarding the material covered in this reading assignment.