Astrophysical evidence on a variety of distance scales clearly shows
that we cannot account for a large fraction of the mass of the
universe. This matter is "dark", not emitting or absorbing any
electromagnetic radiation. A compelling explanation for this missing
mass is the existence of Weakly Interacting Massive Particles (WIMPs).
These particles are well motivated by particle physics theories beyond
the Standard Model, and the discovery of WIMPs would have enormous
impact on both astrophysics and particle physics. WIMPs, if they exist,
would occasionally interact with normal matter. With a mass in the range
of 1 to 1000 times the mass of the proton, and moving at speeds relative
to the Earth of about 220 km/s (the velocity of the Sun around the
MilkyWay), WIMPs would only deposit a small amount of energy when
scattering with nuclei.
Detectors that are low in radioactivity and sensitive to small energy
depositions can search for the rare nuclear recoil events predicted by
WIMP models. In recent years, several new efforts on direct dark matter
detection have begun in which the detection material is a noble
liquid. Advantages include: large nuclear recoil signals in both
scintillation and ionization channels, good scalability to large target
masses, effective discrimination against gamma ray backgrounds, easy
purification, and reasonable cost.
Argonne Physics Division Seminar Schedule