Preflight 4

Reading:

Either: 2009 Particle Data Group review of Dark Matter (Drees & Gerbier)

An up-to-the-minute review of the state of affairs today. The discussion of the experimental situation is somewhat technical (and can be skimmed), but the introductory material should be accessible.

Or: M. de Jesus "Wimp/Neutralino Direct Detection" (astro-ph/0402033)

Similar to the Drees and Gerbier review above, but focuses on WIMPs and particularly neutralinos. Very nicely illustrated. Also somewhat more technical about detection techniques. You can read either this or the Drees and Gerbier paper, though you'll get more out of reading both.

Recommended:

Richard J. Gaitskell, Direct Detection of Dark Matter, 2004, ARNPS

A comprehensive and relatively recent review, with emphasis on experimental techniques. The experimental discussion is more technical, but the astrophysics, cosmology, and theory is clear and approachable.

Questions

The questions are really meant to help guide your thinking as you read. You may find it helpful to look at the questions first and bear them in mind as you read.

1. Non-baryonic dark matter: evidence and candidates.
   1. As discussed in nauseating detail in class, primordial nucleosynthesis has long provided a measure of the cosmic density of baryons; this in turn demands two kinds of dark matter. How do light element abundances imply the need for non-baryonic dark matter? In particular, what would light element abundances be like if the cosmic baryon density were the same as the observed cosmic matter density? How strongly do light element observations rule out this possibility? Hint: you may wish to consult the Schramm plot (and extrapolate if need be).
   2. Why is evidence for non-baryonic dark matter important for elementary particle physics? What properties must non-baryonic dark matter particles have? Of the known, experimentally confirmed particles, which (if any) are candidates for non-baryonic dark matter?
   3. As mentioned briefly in the Drees and Gerbier review, and in more detail elsewhere (e.g., here and in references therein, for those interested) the bullet cluster of galaxies offers particularly vivid evidence for dark matter and its properties. What is the bullet cluster, and what does it teach us about the nature of dark matter?
2. WIMP Properties and Detection.
   1. What is a WIMP? How would WIMPs arise cosmologically?
   2. Why is it expected that dark matter might have weak-scale interactions? That is, why would weakly-interacting particles be more abundant cosmologically than strongly-interacting particles?
   3. Briefly describe the main techniques used to detect WIMPs. Some experiments are already up and running--where are some of the these? Which experiment has claimed strong detection of a WIMP signal?

3. What material did you find difficult, confusing, or unclear? What material would you like to know more about?

4. Other questions or comments?