We report results of a search for weakly interacting massive particles (WIMPS) with the silicon detectors of the CDMS II experiment. This blind analysis of 140.2 kg day of data taken between July ...2007 and September 2008 revealed three WIMP-candidate events with a surface-event background estimate of 0.41(-0.08)(+0.20)(stat)(-0.24)(+0.28)(syst). Other known backgrounds from neutrons and 206Pb are limited to <0.13 and <0.08 events at the 90% confidence level, respectively. The exposure of this analysis is equivalent to 23.4 kg day for a recoil energy range of 7-100 keV for a WIMP of mass 10 GeV/c2. The probability that the known backgrounds would produce three or more events in the signal region is 5.4%. A profile likelihood ratio test of the three events that includes the measured recoil energies gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood occurs for a WIMP mass of 8.6 GeV/c2 and WIMP-nucleon cross section of 1.9×10(-41) cm2.
We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using ...eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ∼10 GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9 GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.
Astrophysical observations indicate that dark matter constitutes most of the mass in our universe, but its nature remains unknown. Over the past decade, the Cryogenic Dark Matter Search (CDMS II) ...experiment has provided world-leading sensitivity for the direct detection of weakly interacting massive particle (WIMP) dark matter. The final exposure of our low-temperature germanium particle detectors at the Soudan Underground Laboratory yielded two candidate events, with an expected background of 0.9 ± 0.2 events. This is not statistically significant evidence for a WIMP signal. The combined CDMS II data place the strongest constraints on the WIMP-nucleon spin-independent scattering cross section for a wide range of WIMP masses and exclude new parameter space in inelastic dark matter models.
Abstract
Context and objectives. Synthetic cannabinoids are illegal drugs of abuse known to cause adverse neurologic and sympathomimetic effects. They are an emerging health risk: 11% of high school ...seniors reported smoking them during the previous 12 months. We describe the epidemiology of a toxicologic syndrome of acute kidney injury associated with synthetic cannabinoids, review the toxicologic and public health investigation of the cluster, and describe clinical implications of the cluster investigation. Materials and methods. Case series of nine patients affected by the toxicologic syndrome in Oregon and southwestern Washington during May-October 2012. Cases were defined as acute kidney injury (creatinine > 1.3 mg/dL) among persons aged 13-40 years without known renal disease who reported smoking synthetic cannabinoids. Toxicology laboratories used liquid chromatography and time-of-flight mass spectrometry to test clinical and product specimens for synthetic cannabinoids, their metabolites, and known nephrotoxins. Public health alerts informed clinicians, law enforcement, and the community about the cluster and the need to be alert for toxidromes associated with emerging drugs of abuse. Results. Patients were males aged 15-27 years (median, 18 years), with intense nausea and flank or abdominal pain, and included two sets of siblings. Peak creatinine levels were 2.6-17.7 mg/dL (median, 6.6 mg/dL). All patients were hospitalized; one required dialysis; none died. No alternate causes of acute kidney injury or nephrotoxins were identified. Patients reported easily purchasing synthetic cannabinoids at convenience, tobacco, and adult bookstores. One clinical and 2 product samples contained evidence of a novel synthetic cannabinoid, XLR-11 (1-(5-fluoropentyl)-1H-indol-3-yl(2,2,3,3-tetramethylcyclopropyl)methanone). Discussion and conclusion. Whether caused by direct toxicity, genetic predisposition, or an as-yet unidentified nephrotoxin, this association between synthetic cannabinoid exposure and acute kidney injury reinforces the need for vigilance to detect new toxicologic syndromes associated with emerging drugs of abuse. Liquid chromatography and time-of-flight mass spectrometry are useful tools in determining the active ingredients in these evolving products and evaluating them for toxic contaminants.
There is a growing interest in cryogenic calorimeters with macroscopic absorbers for applications such as dark matter direct detection and rare event search experiments. The physics of energy ...transport in calorimeters with absorber masses exceeding several grams is made complex by the anisotropic nature of the absorber crystals as well as the changing mean free paths as phonons decay to progressively lower energies. We present a Monte Carlo model capable of simulating anisotropic phonon transport in cryogenic crystals. We have initiated the validation process and discuss the level of agreement between our simulation and experimental results reported in the literature, focusing on heat pulse propagation in germanium. The simulation framework is implemented using Geant4, a toolkit originally developed for high-energy physics Monte Carlo simulations. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that our current work may open up new avenues for applications in material science and condensed matter physics.
Micro-X is a sounding-rocket experiment that will combine a transition edge sensor (TES) microcalorimeter array with an imaging mirror to obtain high-spectral-resolution images of astronomical X-ray ...sources. The instrument's resolution across the 0.3-2.5 keV band will be 2 eV. The first flight will target the region of the Bright Eastern Knot of the Puppis A supernova remnant and is slated for January 2011. The obtained high-resolution X-ray spectra will be used to ascertain the temperature and ionization state of the X-ray-emitting gas and to determine its velocity structure. The TES array is read out by a time-division superconducting quantum interference device (SQUID) multiplexing system. The detector front end assembly and the SQUID multiplexing circuit are cooled to the operating temperature of 50 mK with an adiabatic demagnetization refrigerator (ADR). The design of this refrigerator is tailored to the requirements of rocket flight. Stable operation of the TES array close to the ADR magnet will be achieved with a magnetic shielding system, which will be based on a combination of a bucking coil and high-permeability and superconducting shield materials to cancel out residual fields. We describe our progress in developing the Micro-X instrument.
The SuperCDMS collaboration is presently operating a 9 kg Ge payload at the Soudan Underground Laboratory in their direct search for dark matter. The Ge detectors utilize double-sided athermal phonon ...sensors with an interdigitated electrode structure (iZIPs) to reject near-surface electron-recoil events. These detectors each have a mass of 0.6 kg and were fabricated with photolithographic techniques. The detector fabrication advances required and the production yield encountered are described.
We have recently started to develop a high-resolution gamma-ray spectrometer for material defect analysis. Our gamma-ray detector is a microcalorimeter consisting of an iridium/gold bilayer ...transition edge sensor (TES) thermometer and a bulk Pb absorber, which is directly coupled to a TES with Stycast 2850FT epoxy. This paper describes our TES based gamma-ray detector and the first experimental results for 662 keV and 1173 keV incident gamma-rays. We report an energy resolution of 4.7 keV at 662 keV and 2.9 keV at 1173 keV.
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