Lecturer: Prof. John D. Vergados
Affiliation: Physics Department,
University of Ioannina, Greece
Abstract:
Matter constitutes 30% of the energy
content of the Universe. The remaining
70% is what is called dark energy, which
exhibits unusual repulsive gravitational
interactions.
On the matter sheet, only 5% is of
known nature, i.e. matter such as found
in atoms, in stars, in planets etc. From
observations on all astrophysical and
cosmological scales we know that most
of it, i.e. 25%, is dark matter (DM) of
unknown nature.
The nature of DM is one of the most
important open problems in science. The
ongoing hunt for DM is multi-pronged
and interdisciplinary involving cosmology
and astrophysics, particle and nuclear
physics as well as detector technology.
In this talk we will focus on the direct
detection of the dark matter
constituents, the so called weakly
interacting massive particles (WIMPs), in
underground labs. The detection consists
of measuring the energy deposited in the
detector by the recoiling nucleus, after
its elastic collision with a WIMP (spin
independent or spin induced). In
obtaining the event rates one needs
models about the WIMP interaction and
density in our vicinity as well as its
velocity distribution. No events have so
far been observed, only exclusion plots
on the nucleon cross sections have been
obtained, which will be discussed. Since
the expected rates are very small and
the usual experimental signature is not
different from that of the backgrounds,
we will discuss some special signatures
that might aid in the analysis of the
experiments such as the time
dependence of the signal (modulation
effect) and the option of inelastic
scattering, possible in some special
targets, by detecting γ‐rays following the
de-excitation of the nucleus