Description
In recent years, measurements of the red shift of light from
distant Supernova explosions, new observations of the cosmic
microwave background with unprecedented precision as well as
galaxy redshift surveys of hundreds of thousand of galaxies
have revealed an expanding Universe almost completely filled
with Dark Energy and Dark Matter. Although there are good
motivations from theoretical and experimental particle
physics for the existence of Dark Matter in form of
non-baryonic elementary particles, we have only restricted
or very little information from direct investigations on
these particles.
The two major candidates for Dark Matter particles are the
well-known neutrinos and the yet unknown so-called WIMPs,
weakly interacting massive particles. Whereas the first are
very light and thus considered as “Hot Dark Matter”, WIMPs
are expected to be very massive and would thus be “Cold Dark
Matter”.
The observation of neutrino oscillations is an unambiguous
proof of a non-zero neutrino mass. However, the absolute
mass scale cannot be extracted from such experiments. The
most sensitive laboratory search on the neutrino mass is the
investigation of the kinematics of the ß decay, especially
the decay 3H 3He + e- +anti(e). At the Forschungszentrum
Karlsruhe, the KArlsruhe TRItium Neutrino experiment KATRIN
is under construction to improve the existing sensitivity on
the neutrino mass by more than one order of magnitude down
to 200meV. Thus, KATRIN will be able to decide whether
neutrinos play a significant role in the structure formation
of the early Universe.
About 23% of the Universe´s mass content should be in form
of Cold Dark Matter. WIMPs as particle candidates for this
contribution would have formed the seeds of galaxy formation
in the early Universe and would hence also form the Dark
Halo surrounding our galaxy, the Milky Way. One attempt to
detect them is the measurement of the energy released in
elastic scattering of these halo WIMPs off nuclei of the
detector material. The Forschungszentrum Karlsruhe is
involved in the EDELWEISS direct Dark Matter search
experiment installed in the Laboratoire Souterrain de Modane
in the French-Italian Fréjus tunnel. The detectors used in
EDELWEISS are Ge crystals of 320g mass operated at a
temperature of 17mK.
In this lecture, we shortly review the cosmological
motivation for particle Dark Matter and describe in detail
the physics scheme, the experimental set-ups and technical
challenges for laboratory Dark Matter search with KATRIN and
EDELWEISS.
Author
Dr
Klaus Eitel
