The Particle World

What is dark matter?
How can we make it in the laboratory?

Andreas Albrecht
Andreas Albrecht, University of California – Davis physics professor, talks about one of the current great mysteries of the universe—dark matter.
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Tools for a Scientific Revolution



Scientists are measuring the distribution of dark matter in the universe in a variety of ways: (a) by studying the large-scale distribution of galaxies, as with the Sloan Digital Sky Survey (SDSS); (b) by constraining the dark matter mass power spectrum through weak lensing studies, as by a proposed Large Synoptic Survey Telescope (LSST) and the Joint Dark Energy Mission (JDEM); and (c) by cataloging massive clusters of galaxies as a function of redshift, using the Sunyaev-Zeldovitch effect, by the South Polar Telescope and the Atacame Cosmology Telescope.

What is dark matter? Particle physics models suggest that dark matter is either axions (hypothetical new particles associated with Quantum Chromodynamics ), or WIMPs (hypothetical new particles with weak interactions and TeV-scale masses, natural by-products of theories of supersymmetry or extra dimensions). If dark matter particles are relics from the near-total annihilation in the early universe, simple dimensional analysis suggests that the particles originate from physics at the TeV scale. The particle nature of dark matter can be verified by finding the rare events they would produce in a sensitive underground dark matter detector such as Cryogenic Dark Matter Search . Such experiments may see products of dark matter particles in our galaxy. Annihilation of TeV-scale dark matter particles might be detected as line radiation in high-energy gamma ray telescopes such as GLAST and VERITAS, or possibly in astrophysical neutrino detectors such as IceCube. Antiparticles produced in these annihilations might also be detectable by AMS. If dark matter particles are much more massive, they might produce signals in the ultra-high-energy cosmic rays.


Searches for candidate dark matter particles are underway at present-day colliders. If these particles have masses at the TeV scale, they will surely be discovered at the LHC. Verifying that these new particles are indeed related to dark matter will require a linear collider to characterize their properties. A linear machine would be able to measure the mass, spin and parity of dark matter particles with precision. These results will permit calculation of the present-day cosmic abundance of dark matter and comparison to cosmological observations. If the values agree, it will be a great triumph for both particle physics and cosmology and will extend the understanding of the evolution of the universe back to 1010 seconds after the big bang.