All of the following is from memory. Some of the memory may be faulty, but I think the gist aligns with current theory.

I believe that the relative abundances of light elements in the universe, particularly deuterium, are thought to constrain the amount of baryonic matter, so much so that most of the dark matter must be nonbaryonic (not made from protons and neutrons). Neutrinos are a form of nonbaryonic hot ("hot" meaning very fast moving) dark matter. The leading theory of something called the "strong CP problem" postulates the existence of particles called "axions," that would also be hot. Scientists at CERN and elsewhere are currently conducting axion searches, but the axions, if they exist, are probably too light for present-day technology to find. In any case, many scientists feel that there must also be a tremendous amount of cold nonbaryonic matter (much more than the total amount of baryonic matter) because hot matter wouldn't clump around galaxies and galaxy clusters enough to produce the observed effects.

The idea of the universe containing huge amounts of cold nonbaryonic matter is certainly intriguing. What could it consist of? One interesting set of candidates arises from the theory of supersymmetry, which is central to some unified field theories. According to supersymmetry, to each type of known particle of matter there corresponds a heavier type of force carrying particle, and to each known type of force carrying particle there corresponds a heavier type of particle of matter.

The large hadron collider, scheduled to begin operation in 2007, may discover some supersymmetric particles. In fact, if it doesn't, I believe that this failure will exclude some of the most staightforward unified field theories. A stable, electrically neutral supersymmetric particle might account for cold dark matter.

I find all this very exciting. I anticipate very interesting results from the large hadron collider. As a side note, the CDF collaboration at Fermilab may have just discovered a new resonance (particle) at 500 GEV. I saw this at PhysOrg.com

I think the CMB observations are relevant because, as I remember, they constrain the total mass density of the observable universe. I don't understand why, however.