Silicon Detector Dark Matter Results from the Final Exposure of CDMS II

We report results of a search for weakly interacting massive particles( WIMPS) with the silicon detectors of the CDMS II experiment. This blind analysis of 140.2 kg day of data taken between July 2007 and September 2008 revealed three WIMP-candidate events with a surface-event background estimate of 0.41^(+0.20)_(−0.08)(stat)^(+0.28)_(−0.24)(syst). Other known backgrounds from neutrons and ^(206)Pb are limited to <0.13 and <0.08 events at the 90% confidence level, respectively. The exposure of this analysis is equivalent to 23.4 kg day for a recoilenergy range of 7–100 keV for a WIMPof mass 10  GeV/c^2. The probability that the known backgrounds would produce three or more events in the signal region is 5.4%. A profile likelihood ratio testof the three events that includes the measured recoilenergies gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood occurs for a WIMPmass of 8.6  GeV/c2 and WIMP-nucleon cross section of 1.9×10^(−41)  cm^2.