Class #8 (March 14) Reading Questions - Particle Physics, Secs. 24-29
1. The W and Z particles were first observed in proton-antiproton collisions carried out at the CERN-SPS accelerator. The fundamental "reaction" is usually written as p + pbar -> W + X where X is one or more hadrons. What are the most likely hadrons to be produced? (Draw a Feynman diagram for your process and bring it to class. Look at the weak interaction quark-W vertex shown on pg 75 of the Griffiths handout, noting that you will need to rotate this vertex so the W points to the right.)
2. Explain what is meant by the parton model and how deep inelastic scattering can test this idea. (Can elastic [i.e. Rutherford-like] electron-proton scattering be used to test this model)?
3. What is the physical idea behind the Bjorken scaling hypothesis?
4. The electron-nucleon differential scattering cross-section, given in Fig 26.1, involves two structure functions which provide a way of quantifying the "shape" of the nucleon (i.e., the structure functions gives a measure of the difference between an extended object and a point-like object). Why are there two structure functions in this equation?
5. What is meant by the terms confinement and asymptotic freedom? What is the experimental evidence for these two behaviors?
6. In the Bjorken scaling limit the complicated nucleon structure functions are simply related to each other (see pg 129) and can be written in terms of parton probability functions (see 1st two equations on pg 138). If the proton is made of up and down quarks why are anti-quarks and charm and strange quarks included in Eq. 29.1?
7. The weak and strong interactions "see" different versions of the quarks (i.e. a strongly produced d-quark is seen in a weak interaction as a d*cos(theta_C) + s*sin(theta_C) where theta_C is the Cabbibo angle). How about the weak and electromagnetic interactions ... do they "see" the same quarks? How does one test this experimentally?
Your Question: Please give a well-formulated question that you have regarding the material covered in this reading assignment.