427 research outputs found
A special study of the language and contents of Josephus’ ‘Jewish Antiquities’ books XI - XX
Not availabl
Investigation of charge coupled device correlation techniques
Analog Charge Transfer Devices (CTD's) offer unique advantages to signal processing systems, which often have large development costs, making it desirable to define those devices which can be developed for general system's use. Such devices are best identified and developed early to give system's designers some interchangeable subsystem blocks, not requiring additional individual development for each new signal processing system. The objective of this work is to describe a discrete analog signal processing device with a reasonably broad system use and to implement its design, fabrication, and testing
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature 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. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of 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 in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.Comment: 40 pages, 49 figures (4 in color), submitted to Phys. Rev. D;
v.2:clarified conclusions, added content and references based on referee's
and readers' comments; v.3: clarified introductory sections, added figure
based on referee's comment
Nuclear Shell Model Calculations of Neutralino-Nucleus Cross Sections for Silicon 29 and Germanium 73
We present the results of detailed nuclear shell model calculations of the
spin-dependent elastic cross section for neutralinos scattering from \si29 and
\ge73. The calculations were performed in large model spaces which adequately
describe the configuration mixing in these two nuclei. As tests of the computed
nuclear wave functions, we have calculated several nuclear observables and
compared them with the measured values and found good agreement. In the limit
of zero momentum transfer, we find scattering matrix elements in agreement with
previous estimates for \si29 but significantly different than previous work for
\ge73. A modest quenching, in accord with shell model studies of other heavy
nuclei, has been included to bring agreement between the measured and
calculated values of the magnetic moment for \ge73. Even with this quenching,
the calculated scattering rate is roughly a factor of 2 higher than the best
previous estimates; without quenching, the rate is a factor of 4 higher. This
implies a higher sensitivity for germanium dark matter detectors. We also
investigate the role of finite momentum transfer upon the scattering response
for both nuclei and find that this can significantly change the expected rates.
We close with a brief discussion of the effects of some of the non-nuclear
uncertainties upon the matrix elements.Comment: 31 pages, figures avaiable on request, UCRL-JC-11408
Low-threshold analysis of CDMS shallow-site data
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.Comment: 18 pages, 12 figures, 5 table
The CRESST Dark Matter Search
The current status of CRESST (Cryogenic Rare Event Search using
Superconducting Thermometers) and new results concerning the detector
development are presented. The basic technique of CRESST is to search for
particle Dark Matter (WIMPS, Weakly Interacting Massive particles) by the
measurement of non-thermal phonons as created by WIMP-induced nuclear recoils.
Combined with the newly developed method of simultaneous measurement of
scintillation light, strong background discrimination is possible, resulting in
a substantial increase in WIMP detection sensitivity. The short and long term
perspectives of CRESST are discussed.Comment: 12 pages, 6 figure
After LUX: The LZ Program
The LZ program consists of two stages of direct dark matter searches using
liquid Xe detectors. The first stage will be a 1.5-3 tonne detector, while the
last stage will be a 20 tonne detector. Both devices will benefit tremendously
from research and development performed for the LUX experiment, a 350 kg liquid
Xe dark matter detector currently operating at the Sanford Underground
Laboratory. In particular, the technology used for cryogenics and electrical
feedthroughs, circulation and purification, low-background materials and
shielding techniques, electronics, calibrations, and automated control and
recovery systems are all directly scalable from LUX to the LZ detectors.
Extensive searches for potential background sources have been performed, with
an emphasis on previously undiscovered background sources that may have a
significant impact on tonne-scale detectors. The LZ detectors will probe
spin-independent interaction cross sections as low as 5E-49 cm2 for 100 GeV
WIMPs, which represents the ultimate limit for dark matter detection with
liquid xenon technology.Comment: Conference proceedings from APS DPF 2011. 9 pages, 6 figure
Radiogenic and Muon-Induced Backgrounds in the LUX Dark Matter Detector
The Large Underground Xenon (LUX) dark matter experiment aims to detect rare
low-energy interactions from Weakly Interacting Massive Particles (WIMPs). The
radiogenic backgrounds in the LUX detector have been measured and compared with
Monte Carlo simulation. Measurements of LUX high-energy data have provided
direct constraints on all background sources contributing to the background
model. The expected background rate from the background model for the 85.3 day
WIMP search run is
~events~keV~kg~day
in a 118~kg fiducial volume. The observed background rate is
~events~keV~kg~day,
consistent with model projections. The expectation for the radiogenic
background in a subsequent one-year run is presented.Comment: 18 pages, 12 figures / 17 images, submitted to Astropart. Phy
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