where
f
is the quenching factor which reflects the relative efficiency
with which the nuclear recoil energy is recorded in the signal
channel compared to a
-ray of the same energy.
is the characteristic energy for the virialized WIMP population,
F
is the form factor referred to previously, and
r
is a kinematic factor dependent on the relative masses of the
WIMP and target nuclei. Somewhat more complex formulae result
when modified velocity distributions are used (e.g.
incorporating a Galactic cut-off), or the rate is convolved
through the instrument response. A falling recoil spectrum with a
maximum recoil energy
is expected. For larger target nuclei, such as iodine, the form
factor further suppresses the recoil spectrum above
50 keV.
Inelastic WIMP scattering (producing excited nuclear states)
can also occur.
-rays emitted from nuclear relaxation can be self-absorbed in
the detector producing characteristic spectral lines. Experiments
of this sort have been performed [15,
52,
18]; the cross-sections are much lower than the elastic ones and
the technique will not be discussed further.
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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 |