Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four ∼224 g germanium and two ∼105 g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of ∼1 keV and ∼2 keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9 GeV/c 2 . Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments' data as WIMP signals, and exclude new parameter space for WIMP masses between 3 GeV/c 2 and 4 GeV/c 2 .PACS numbers: 14.80. Ly, 95.35.+d, 95.30.Cq, 85.25.Oj, 29.40.Wk

The Cryogenic Dark Matter Search (CDMS) is an experiment to detect weakly interacting massive particles (WIMPs), which may constitute the universe's dark matter, based on their interactions with Ge and Si nuclei. We report the results of an analysis of data from the first two runs of CDMS at the Soudan Underground Laboratory in terms of spin-dependent WIMP-nucleon interactions on 73 Ge and 29 Si. These data exclude new regions of WIMP parameter space, including regions relevant to spin-dependent interpretations of the annual modulation signal reported by the DAMA/NaI experiment. DOI: 10.1103/PhysRevD.73.011102 PACS numbers: 95.35.+d, 14.80.Ly The nature of the dark matter which dominates structure formation in our universe is one of the most pressing questions of modern cosmology [1][2][3]. A promising class of candidates is weakly interacting massive particles (WIMPs) [4], particularly the lightest neutralino in supersymmetric (SUSY) extensions to the standard model [3]. Many groups have sought to detect WIMPs directly via their elastic scattering off atomic nuclei [5].The nucleon coupling of a slow-moving Majorana neutralino (or of any WIMP in the extreme nonrelativistic limit [6]) is characterized by two terms: spin-independent (e.g. scalar) and spin-dependent (e.g. axial vector). When coherence across the nucleus is taken into account [7], these two terms behave very differently. The neutralino has similar scalar couplings to the proton and neutron [3], and nucleon contributions interfere constructively to enhance the WIMP-nucleus elastic cross section. Thus, though neutralino-nucleon cross sections for such interactions are generally orders of magnitude smaller than in the axial case [8], scalar couplings dominate direct-detection event rates in most SUSY models for experiments using heavy target nuclides.In contrast, the axial couplings of nucleons with opposing spins interfere destructively, leaving WIMP scattering amplitudes determined roughly by the unpaired nucleons (if any) in the target nucleus. Spin-dependent WIMP couplings to nuclei thus do not benefit from a significant coherent enhancement, and sensitivity to such interactions requires the use of target nuclides with unpaired neutrons or protons. Spin-dependent interactions may nonetheless dominate direct-detection event rates in spin-sensitive experiments in regions of parameter space where the scalar coupling is strongly suppressed. This can provide a lower bound on the total WIMP-nucleus elastic cross section, since spin-dependent amplitudes are more robust against fine cancellations [9]. In general, consideration of such couplings when interpreting experimental results more fully constrains WIMP parameter space and allows exploration of alternative interpretations of possible signals [10,11]. In this work we explore the implications of recent results from the Cryogenic Dark Matter Search (CDMS) * Deceased PHYSICAL REVIEW D 73, 011102(R) (2006)

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We have developed a detector, consisting of a cryogenic calorimeter with a scintillating crystal as absorber, and a second calorimeter for the detection of the scintillation light, both operated at 12 mK. Using a CaWO 4 crystal with a mass of 6 g as

Using improved Ge and Si detectors, better neutron shielding, and increased counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained stricter limits on the cross section of weakly interacting massive particles (WIMPs) elastically scattering from nuclei. Increased discrimination against electromagnetic backgrounds and reduction of the neutron flux confirm WIMPcandidate events previously detected by CDMS were consistent with neutrons and give limits on spin-independent WIMP interactions which are > 2× lower than previous CDMS results for high WIMP mass, and which exclude new parameter space for WIMPs with mass between 8-20 GeV c −2 .PACS numbers: 26.65.+t, 95.75.Wx, 14.60.St This Letter reports new exclusion limits from the Cryogenic Dark Matter Search (CDMS) experiment on the wide class of nonluminous, nonbaryonic, weakly interacting massive particles (WIMPs) [1, 2] which could constitute most of the matter in the universe [3]. A natural WIMP candidate is provided by supersymmetry in the form of the stable lightest superpartner, usually taken to be a neutralino of typical mass ∼ 100 GeV/c 2 [2, 4]. Since the WIMPs are expected to be in a roughly isothermal halo within which the visible portion of our galaxy resides, the energy given to a Ge or Si detector nucleus scattered elastically by a WIMP would be only a few to tens of keV [5].Because of this low recoil energy and very low event rate (< 1 event per day per kg of detector mass), it is essential to suppress backgrounds drastically. The CDMS detectors discriminate nuclear recoils (such as would be produced by WIMPs) from electron recoils by measuring both ionization and phonon energy, greatly reducing the otherwise dominant electromagnetic background. The ionization is much less for nuclear than for electron recoils, while the phonon signal enables a determination of the recoil energy. The main remaining background is from neutrons, which produce WIMP-like recoils, and hence must be distinguished by other means. Two are employed: 1) while Ge and Si have similar scattering rates per nucleon for neutrons, Ge is 5-7 times more efficient than Si for coherently scattering WIMPs; 2) a single WIMP will not scatter in more than one detector, while a neutron frequently will.While brief reviews of all parts of the experiment are provided below, most details have been published [6], and therefore the emphasis here will be on the differences from previous work. The previously published results are from three 165 g Ge BLIP (Berkeley Large Ionization-and-Phonon-mediated) and one 100 g Si ZIP (Z-sensitive Ionization and Phonon-mediated) detectors. The latter, employed as one measure of background neutrons, was not used simultaneously with the Ge BLIPs, but rather in a separate run. BLIP detectors determine phonon production from the detector's calorimetric temperature change, whereas ZIP detectors [7] collect athermal phonons to provide both phonon production and position information. Position information can be obtained