First Results from the Cryogenic Dark Matter Search in the Soudan Underground Laboratory

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6live days, providing 19.4kg d of Ge net exposure after cuts for recoil energies between 10 and 100keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross section for all WIMP masses above 15 GeV/c², ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4×10^-43 cm² at a WIMP mass of 60 GeV/c².