276 Dark matter search with innovative techniques
Figure 8.1.Discrimination capability of the CDMS experiment.the parameterRin (8.5) is given by the slope of the bands. Even in this case, the
total detector mass can be increased only through the realization of a large array
of independent devices, which should be operated underground, for example in
the Gran Sasso Laboratory (Italy).
8.3.3 Discussion of the CDMS results
The CDMS collaboration was able to perform up to now the most sensitive
experiment in terms of exclusion plot [24] (see figure 8.4). This shows clearly the
potential of the double readout technique based on phonon-mediated detection.
The CDSM experiment, even if largely preliminary, is particularly important
since it allows us to probe, at least partially, the region in the(ξσp,Mχ)plane
corresponding to the modulation evidence claimed by the Italian collaboration
DAMA [28]. I shall just recall here that this modulation evidence can be
interpreted in terms of halo neutralino interactions with the most probable values
ofMχ=44 GeV andξσp= 5. 4 × 10 −^41 cm^2. The corresponding 3σregion is
reported in figure 8.4.
The CDMS detectors are operated at Stanford beneath only a 16 m water
equivalent overburden. A plastic scintillator veto is therefore necessary in order
to reject cosmic ray events. The results are based on two data-sets:
- Two month exposure in 1998, providing 33 live days collected with one100 g
Si detectoroperated with a W–Al film phonon readout (see previous section).