The first results from the Cryogenic Dark Matter Search for weakly interacting massive particles (WIMP) in the Soudan Underground Laboratory, were investigated. Four Ge and two Si detectors were operated for about 52.6 live days, which provided 19.4 kg d of Ge net exposure after cuts for recoil energies of range between 10 and 100 keV. To define the energy threshold and selection criteria for nuclear-recoil candidates, a blind analysis was performed. These data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross section for all WIMP masses above 15 GeV/c 2. The results show that the minimum of this limit at the 90% C.L. is 4×10-43 cm2 at a WIMP mass of 60 GeV/c 2.
Bibliographical noteFunding Information:
This work is supported by the National Science Foundation under Grant No. AST-9978911, by the Department of Energy under Contracts No. DE-AC03-76SF00098, No. DE-FG03-90ER40569, and No. DE-FG03-91ER40618, and by Fermilab, operated by the Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the Department of Energy. The ZIP detectors were fabricated in the Stanford Nanofabrication Facility operated under NSF. We are grateful to the Minnesota Department of Natural Resources and the staff of the Soudan Underground Laboratory for their assistance.