Search

The Cryogenic Dark Matter Search (CDMS) uses low-temperature Ge and Si detectors to search for Weakly Interacting Massive Particles (WIMPs) via their elastic-scattering interaction with atomic nuclei while discriminating against interactions of background particles. CDMS data from 1998 and 1999 with a relaxed fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent with an earlier analysis with a more restrictive fiducial-volume cut. Twenty-three WIMP candidate events are observed, but these events are consistent with a background from neutrons. Resulting limits on the spin-independent WIMP-nucleon elastic-scattering cross-section are lower than those of any other experiment for WIMPs with masses between 10–70 GeV c −2 . Under the assumptions of standard WIMP interactions and a standard halo, the results are incompatible with the annual-modulation signal of DAMA at 99.99% CL in the asymptotic limit.

D.S. Akerib, M.S. Armel-Funkhouser, M.J. Attisha, L. Baudis, D.A. Bauer, P.L. Brink, R. Bunker, B. Cabrera, D.O. Caldwell, C.L. Chang, M.B. Crisler, P. Cushman, R. Dixon, M.R. Dragowsky, D.D. Driscoll, L. Duong, R. Ferril, J. Filippini, R.J. Gaitskell, D. Holmgren, M.E. Huber, S. Kamat, A. Lu, R. Mahapatra, V. Mandic, P. Meunier, N. Mirabolfathi, H. Nelson, R. Nelson, R.W. Ogburn, T.A. Perera, E. Ramberg, W. Rau, A. Reisetter, R.R. Ross, T. Saab, B. Sadoulet, J. Sander, C. Savage, R.W. Schnee, D.N. Seitz, B. Serfass, A.J. Sirois, K.M. Sundqvist, J-P.F. Thompson, G. Wang, S. Yellin, and B.A. Young

The CDMS‐II collaboration’s Cold Dark Matter search presently sets the most competitive exclusion limit in the world for the direct detection of the hypothesized Weakly Interacting Massive Particles (WIMPs) that constitute the cold dark matter of the Universe. Our experiment utilizes Ge (and Si) crystals as the target detectors, each with a mass of 250 g (100 g) and cooled to 30 mK. To eliminate natural radioactive sources as background the experiment is conducted in a well‐shielded environment in the Soudan Mine, Minnesota, and has been operating for the last two years. To aid in the identification of a possible WIMP‐candidate event, the detectors are designed to measure both the ionization and athermal phonon signals produced by each candidate event. The athermal phonon signal is measured using superconducting aluminum films on the crystal surface connected to tungsten transition edge sensors. The latest WIMP‐search results from Soudan will be presented, along with projections for the future.

The Cryogenic Dark Matter Search (CDMS) is an experiment to detect weakly interacting massive particles (WIMPs) 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 73Ge and 29Si. These data exclude new regions of spin-dependent WIMP-nucleon interaction parameter space, including regions relevant to spin-dependent interpretations of the annual modulation signal reported by the DAMA/NaI experiment., Comment: 5 pages, 4 figures; replacement to match published version

The Cryogenic Dark Matter Search (CDMS-II) employs low-temperature Ge and Si detectors to seek Weakly Interacting Massive Particles (WIMPs) via their elastic scattering interactions with nuclei. Simultaneous measurements of both ionization and phonon energy provide discrimination against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with >99.99% efficiency. Electromagnetic events very near the detector surface can mimic nuclear recoils because of reduced charge collection, but these surface events are rejected with >96% efficiency by using additional information from the phonon pulse shape. Efficient use of active and passive shielding, combined with the the 2090 m.w.e. overburden at the experimental site in the Soudan mine, makes the background from neutrons negligible for this first exposure. All cuts are determined in a blind manner from in situ calibrations with external radioactive sources without any prior knowledge of the event distribution in the signal region. Resulting efficiencies are known to ~10%. A single event with a recoil of 64 keV passes all of the cuts and is consistent with the expected misidentification rate of surface-electron recoils. Under the assumptions for a standard dark matter halo, these data exclude previously unexplored parameter space for both spin-independent and spin-dependent WIMP-nucleon elastic scattering. The resulting limit on the spin-independent WIMP-nucleon elastic-scattering cross-section has a minimum of 4x10^-43 cm^2 at a WIMP mass of 60 GeV/c^2. The minimum of the limit for the spin-dependent WIMP-neutron elastic-scattering cross-section is 2x10^-37 cm^2 at a WIMP mass of 50 GeV/c^2., 37 pages, 42 figures

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg-d of Ge net exposure after cuts for recoil energies between 10--100 keV. 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, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10^{-43} cm^2 at a WIMP mass of 60 GeV., Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett; minor clarifications in response to referee's comments

The CDMS experiment utilizes Ge and Si detectors operating at 20 mK to search for the Dark Matter of the Universe hypothesized to exist in the form of weakly interacting massive particles (WIMPs). In early 2000, CDMS set the most competitive exclusion limit for scalar-interaction WIMPs in the Stanford Underground Facility (SUF). A new search (CDMS II) is now commencing with several improvements: a deep-site facility in the Soudan mine, Minnesota; and the detector technology has been further improved to aid in the rejection of surface-electron (β) events. A new generation of detectors, sensitive to the initial athermal phonon flux from a particle event, have been in operation for the past year at Stanford's shallow site and are ready for installation at the deep site.