

In the following section it will be seen that we do not yet
understand what determines the gravitational potentials within
the Universe on scales from galaxies upwards. One suggestion is
that the Universe is full of material that does not emit
electromagnetic radiation and which is thus hard to `see'. There
are a tremendous number of ideas on offer to resolve the dark
matter dilemma. These ideas cover modifications to the laws of
gravity, cold conventional matter, new particles, neutrinos with
non-zero mass, and exotic objects, to name just a few. These will
be discussed in more detail later. At the moment, there is no
absolutely clear solution, although a number of the possibilities
do lend themselves to experimental ``searches','' which are being
carried out around the world. Some of the experiments are
designed to look for direct signatures,
i.e.
the physical interaction of a dark matter particle in a
detector, while others are looking for indirect evidence, such as
the neutrino or
-ray flux due to dark matter particle annihilations. In
addition, other types of experiments are looking for
circumstantial evidence, such as the measurement of a non-zero
neutrino mass in the right range, or confirmation of
supersymmetry (SUSY). A number of the direct and indirect
searches will be digging deeply into theoretically very
interesting regions of parameter space over the next five years.
Indeed there is, at this time, one experimental result from a
direct search that has a signal consistent with the most
optimistic SUSY predictions concerning neutralinos - which just
might be proven correct. While it is true to say that most
activity is currently targeted at what might be called the
standard cosmological model, this model is not without its
difficulties as a theory, and experimental evidence from
dedicated dark matter searches could be crucial in finally
clarifying the situation. Experimental searches probably are the
only way to find out unambiguously what the Milky Way is made of.
The evidence is reviewed in section
2, including subsection
2.2
on the standard cosmological model. The candidates are presented
in section
3
. This leads to section
4
on direct and indirect detection requirements and techniques for
non-baryonic dark matter. Most experiments are being carried out
in the context of theoretical expectations for the neutralino,
which most regard as the best motivated of the particle
candidates. Section
5
looks in detail at the requirements for detection of the
neutralino. A review of the current status of projects world-wide
will be given in section
6
. Finally, in section
7
there is a discussion of the next logical steps for experimental
searches for dark matter.


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Experimental Searches for Dark Matter
Timothy J. Sumner
http://www.livingreviews.org/lrr-2002-4
© Max-Planck-Gesellschaft. ISSN 1433-8351
Problems/Comments to
livrev@aei-potsdam.mpg.de
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