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...

Normal conductor-insulator-superconductor ͑NIS͒ junctions promise to be interesting for x-ray and phonon sensing applications, in particular due to the expected self-cooling of the N electrode by the tunneling current. Such cooling would enable the operation of the active element of the sensor below the cryostat temperature and at a correspondingly higher sensitivity. It would also allow the use of NIS junctions as microcoolers. At present, this cooling has not been realized in large area junctions ͑suitable for a number of detector applications͒. In this article, we discuss a detailed modeling of the heat flow in such junctions; we show how the heat flow into the normal electrode by quasiparticle back-tunneling and phonon absorption from quasiparticle pair recombination can overcompensate the cooling power. This provides a microscopic explanation of the self-heating effects we observe in our large area NIS junctions. The model suggests a number of possible solutions.

A prototype weakly interacting massive particle (WIMP) detector system is described. The detection efficiency is much larger when the incident neutral particle flux is perpendicular to the detector plane than when it is parallel to the plane. A greatly scaled-up system based on this device would therefore be sensitive to the diurnal rotation of the "WIMP wind" produced by the solar system's rapid motion through the galactic halo. Experimental results are reported which exhibit the detection efficiency anisotropy when neutrons were used to simulate the interactions of WIMPS.

Genetic analyses of coat colors are frequently restricted to subjectively categorized phenotype information. The aim of this study was to develop a method to numerically quantify the variability of leopard complex (LP) spotting phenotypes introducing tools from image analysis. Generalized Procrustes analysis eliminates systematic errors due to imaging process. The binarization of normalized images and the application of principal component analysis (PCA) on the derived pixel matrices, transform pixel information into numerical data space. We applied these methods on 90 images to ascertain the specific leopard patterns within the Noriker breed. Furthermore, we genotyped a representative sample of 191 Noriker horses for the known LP spotting associated loci. Ninety-seven percentage of the genotyped leopard spotted horses were heterozygous for LP and had at least one copy of the PATN1 allele. However, the remaining pattern variation was great, indicating other genetic factors influencing the expression of LP spotting. Based upon this data, we estimated effect sizes of the modifier PATN1, and additional factors including sex, age, base color, and spotting phenotype of parents. The PCA of the pixel matrix resulted in 2 significant components accounting for 51% of the variation. Applying a linear model, we identified significant effects for age groups and base color on the first and second components, while for sex and parents' LP phenotype significant effects were found on 4 additional components.