Dr. F. Pröbst (MPI München, CRESST Collaboration)
Mardi 29 Novembre 2011 à 14h
CRESST-II is searching for Dark Matter WIMPs via elastic scattering off atomic nuclei in scintillating
CaWO4 target crystals. CRESST has completed more than 730 kg days of data taking in 2011. The data
collected with eight detector modules will be presented, each with a two-channel readout ; one for a
phonon signal and the other for the simultaneously produced scintillation light. The phonon channel
provides a precise measurement of the energy deposited in the crystal by an interaction, while the ratio
of scintillation light to deposited energy serves to distinguish possible signal events from the dominant
backgrounds, and, to a certain extent also to determine the type of nucleus which was recoiling.
67 events are found in the acceptance region where a WIMP signal in the form of low energy nuclear
recoils would be expected. We estimate background contributions to this observation using a maximum
likelihood analysis, and find at a high statistical significance that these background sources alone are
not su cient to explain the data. The addition of a signal due to scattering ffi of relatively light WIMPs
could account for this discrepancy, and we determine the associated WIMP parameters.