You can change this website in over 66 languages

Our Energenius Life "Time"

2-5 a
Direct detection

Further information: Weakly interacting massive particles § Direct detection
Direct detection experiments aim to observe low-energy recoils (typically
a few keVs) of nuclei induced by interactions with particles of dark matter,
which (in theory) are passing through the Earth. After such a recoil the
nucleus will emit energy in the form of scintillation light or phonons, as
they pass through sensitive detection apparatus. To do this effectively, it
is crucial to maintain a low background, and so such experiments operate
deep underground to reduce the interference from cosmic rays. Examples
of underground laboratories with direct detection experiments include the
Stawell mine, the Soudan mine, the SNOLAB underground laboratory at
Sudbury, the Gran Sasso National Laboratory, the Canfranc Underground
Laboratory, the Boulby Underground Laboratory, the Deep Underground
Science and Engineering Laboratory and the China Jinping Underground
Laboratory.
These experiments mostly use either cryogenic or noble liquid detector
technologies. Cryogenic detectors operating at temperatures below 100 mK,
detect the heat produced when a particle hits an atom in a crystal absorber
such as germanium. Noble liquid detectors detect scintillation produced
by a particle collision in liquid xenon or argon. Cryogenic detector experiments
include: CDMS, CRESST, EDELWEISS, EURECA. Noble liquid
experiments include ZEPLIN, XENON, DEAP, ArDM, WARP, DarkSide,
PandaX, and LUX, the Large Underground Xenon experiment. Both of
these techniques focus strongly on their ability to distinguish background
particles (which predominantly scatter off electrons) from dark matter
particles (that scatter off nuclei). Other experiments include SIMPLE and
PICASSO.
Currently there has been no well-established claim of dark matter detection
from a direct detection experiment, leading instead to strong upper limits
on the mass and interaction cross section with nucleons of such dark matter
particles. The DAMA/NaI and more recent DAMA/LIBRA experimental
collaborations have detected an annual modulation in the rate of events in
their detectors, which they claim is due to dark matter. This results from
the expectation that as the Earth orbits the Sun, the velocity of the detector
relative to the dark matter halo will vary by a small amount. This claim is
so far unconfirmed and in contradiction with negative results from other
experiments such as LUX, SuperCDMS and XENON100.
A special case of direct detection experiments covers those with directional
sensitivity. This is a search strategy based on the motion of the Solar System
around the Galactic Center. A low-pressure time projection chamber
makes it possible to access information on recoiling tracks and constrain
WIMP-nucleus kinematics. WIMPs coming from the direction in which the
Sun travels (approximately towards Cygnus) may then be separated from
background, which should be isotropic. Directional dark matter experiments
include DMTPC, DRIFT, Newage and MIMAC.