Class #6 (Feb. 14) Reading Questions - Particle Physics, Secs. 15-18, Handout pgs. 71-79

1. Explain how the vertices and diagrams from the Fermi theory of the weak interaction (shown in Figs. 15.1 and 17.1 of our text) are similar to and different from the Feynman vertices and diagrams for weak processes (shown on pgs. 74-75 of the Griffiths handout).

2. Scattering cross-section is a measure of the effective "area" of a target object in a collision type interaction (thus, hard spheres have a scattering cross-section = pi*D^2 where D=diameter). Compare the neutrino cross-section constant given on pg. 90 to the cross-sectional area of a proton. According to the Fermi theory, neutrino scattering cross-sections increase with energy. How do we know this prediction cannot be completely correct?

3. What is measured by the Cabibbo angle? How is this angle related to the Kobayashi-Maskawa matrix given on pg. 78 of Griffiths?

4. What is the major difference between the allowed leptonic and the allowed hadronic (i.e., quark-quark) Feynman diagram vertices for the weak interaction?

5. What is a W particle? What types of interactions can a W participate in? What feature of the old Fermi theory tells us that the W particle must have a large mass?

6. What is the role of neutrinos in stellar processes and stellar evolution? Would stars behave differently if they produced only photons and no neutrinos?

[For anyone interested in astrophysics, look up SN1987A and comment on its role in our understanding of neutrino physics and supernovae].

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