The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. CDMS data, accounting for the neutron background, give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above 10 GeV͞c 2 WIMP mass and, at .75% C.L., the entire 3s allowed region for the WIMP signal reported by the DAMA experiment. Extensive evidence indicates that a large fraction of the matter in the universe is nonluminous, nonbaryonic, and "cold"-nonrelativistic at the time matter began to dominate the energy density of the universe [1][2][3]. Weakly interacting massive particles (WIMPs) are an excellent candidate for nonbaryonic, cold dark matter [2,4]. Minimal supersymmetry provides a natural WIMP candidate in the form of the lightest superpartner, with a typical mass M ϳ 100 GeV͞c 2 [5][6][7][8]. WIMPs are expected to have collapsed into a roughly isothermal, spherical halo within which the visible portion of our galaxy resides. WIMPs scatter off nuclei via the weak interaction, potentially allowing their direct detection [9,10]. The expected spectrum of recoil energies (energy given to the recoiling nucleus during the interaction) is exponential with a characteristic energy of a few to tens of keV [11]. The expected event rate is model dependent, but is generically 1 kg 21 d 21 or lower [10].This Letter reports new exclusion limits on the spinindependent WIMP-nucleon elastic-scattering cross section by the Cryogenic Dark Matter Search (CDMS). The rate of rare WIMP-nucleon interactions is constrained by extended exposure of detectors that discriminate WIMPinduced nuclear recoils from electron recoils caused by interactions of background particles [12,13].The ionization yield Y (the ratio of ionization production to recoil energy in a semiconductor) of a particle interaction differs greatly for nuclear and electron recoils. CDMS detectors measure phonon and electron-hole pair production to determine recoil energy and ionization yield for each event. The data discussed here were obtained with two types of detectors, Berkeley Large Ionization-and Phonon-mediated (BLIP) and Z-sensitive Ionization-and Phonon-mediated (ZIP) detectors [12][13][14][15][16][17][18]. For both types, the drift field for the ionization measurement is supplied by radially segmented electrodes on the faces of the disk-shaped crystals [19]. In BLIP detectors, phonon production is determined from the detector's calorimetric temperature change. In ZIP detectors, athermal phonons are collected to determine phonon production and xy position. Detector performance is discussed in detail elsewhere [14,[16][17][18][19][20].Photons cause most bulk electron recoils, while lowenergy electrons incident on the detector surfaces cause low-Y electron recoils in a thin surface layer ("surface events"). Neutron, photon, and electron sources ar...

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The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated the large potential of double beta decay to search for new physics beyond the standard model. To increase by a major step the present sensitivity for double beta decay and dark matter search, much bigger source strengths and much lower backgrounds are needed than used in experiments under operation at present or under construction. We describe here a project which would operate one tonne of 'naked' enriched germanium-detectors in liquid nitrogen as shielding in an underground set-up (GENIUS). It improves the sensitivity of neutrino masses to 0.01 eV. A 10 tonne version would probe neutrino masses even down to 10 −3 eV. The first version would allow us to test the atmospheric neutrino problem, the second at least part of the solar neutrino problem. Both versions would allow, in addition, significant contributions to testing several classes of GUT models. These are especially tests of R-parity breaking and conserving supersymmetry models-including sneutrino masses-leptoquark masses and mechanism and right-handed W-boson masses comparable with LHC. The second issue of the experiment is the search for dark matter in the universe. The full MSSM parameter space for the prediction of neutralinos as dark matter particles could be covered already in a first step of the full experiment using only 100 kg of 76 Ge or even of natural Ge making the experiment competitive with LHC in the search for supersymmetry.

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

The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated the large potential of double beta decay to search for new physics beyond the Standard Model. To increase by a major step the present sensitivity for double beta decay and dark matter search much bigger source strengths and much lower backgrounds are needed than used in experiments under operation at present or under construction. We present here a study of a project proposed recently [1], which would operate one ton of 'naked' enriched GErmanium-detectors in liquid NItrogen as shielding in an Underground Setup (GENIUS). It improves the sensitivity to neutrino masses to 0.01 eV. A ten ton version would probe neutrino masses even down to 10 −3 eV. The first version would allow to test the atmospheric neutrino problem, the second at least part of the solar neutrino problem. Both versions would allow in addition significant contributions to testing several classes of GUT models. These are especially tests of R-parity breaking supersymmetry models, leptoquark masses and mechanism and right-handed W-boson masses comparable to LHC. The second issue of the experiment is the search for dark matter in the universe. The entire MSSM parameter space for prediction of neutralinos as dark matter particles could be covered already in a first step of the full experiment with the same purity requirements, but using only 100 kg of 76 Ge or even of natural Ge making the experiment competitive to LHC in the search for supersymmetry.The layout of the proposed experiment is discussed and the shielding and purity requirements are studied using GEANT Monte Carlo simulations. As a demonstration of the feasibility of the experiment first results of operating a 'naked' Ge detector in liquid nitrogen are presented.