New Results on Direct Detection of Cosmic Dark Matter

Saturday, 15 February 2014
Regency C (Hyatt Regency Chicago)
Dan Bauer , Fermilab, Batavia, IL
An overwhelming body of evidence from many types of astronomical
observations suggests that most of the matter in the universe is of a
type that neither emits nor absorbs electromagnetic radiation. While we
know very little about the nature of this "dark matter", particle
physics provides many possibilities. The most compelling theory is that
dark matter is made up of Weakly Interacting Massive Particles (WIMPs).

Dark matter clearly responds to gravitational forces, and cosmological
simulations imply that it provided the scaffolding on which normal
matter coalesced into galaxies. If true, this implies that all galaxies,
including our own, are embedded within an enormous cloud of dark matter.
The solar system is then encountering a dark matter "wind" as it
revolves around the galactic center. If WIMPs indeed make up the dark
matter, they are raining down continually on the earth. However, since
they interact only very weakly with normal matter, they mostly pass
right through us. Very occasionally, one may bump into an atomic nucleus
and give it a small kick. If one could measure the energy imparted by
such an event, and distinguish it from the overwhelming energy deposited
by normal particle interactions, WIMPs could be detected directly in the
laboratory. Many technologies have been explored to provide this
discrimination between WIMPs and normal particles, including ultrapure
solid-state crystals cooled to near absolute zero in order to detect
heat liberated by recoiling particles, bubble chambers that respond only
to localized energy depositions and liquefied noble elements (primarily
Argon and Xenon) that produce light in response to particle

In this talk, I will present the current status of direct detection
experiments searching for WIMP dark matter. Although there is currently
no confirmed evidence for WIMPS, there have been numerous hints in
recent years, giving a sense that we may be closing in on an
understanding of dark matter.