156 research outputs found
Results from 730 kg days of the CRESST-II Dark Matter Search
The CRESST-II cryogenic Dark Matter search, aiming at detection of WIMPs via
elastic scattering off nuclei in CaWO crystals, completed 730 kg days of
data taking in 2011. We present the data collected with eight detector modules,
each with a two-channel readout; one for a phonon signal and the other for
coincidently produced scintillation light. The former provides a precise
measure of the energy deposited by an interaction, and the ratio of
scintillation light to deposited energy can be used to discriminate different
types of interacting particles and thus to distinguish possible signal events
from the dominant backgrounds. Sixty-seven events are found in the acceptance
region where a WIMP signal in the form of low energy nuclear recoils would be
expected. We estimate background contributions to this observation from four
sources: 1) "leakage" from the e/\gamma-band 2) "leakage" from the
\alpha-particle band 3) neutrons and 4) Pb-206 recoils from Po-210 decay. Using
a maximum likelihood analysis, we find, at a high statistical significance,
that these sources alone are not sufficient to explain the data. The addition
of a signal due to scattering of relatively light WIMPs could account for this
discrepancy, and we determine the associated WIMP parameters.Comment: 17 pages, 13 figure
The CRESST II Dark Matter Search
Direct Dark Matter detection with cryodetectors is briefly discussed, with
particular mention of the possibility of the identification of the recoil
nucleus. Preliminary results from the CREEST II Dark Matter search, with 730
kg-days of data, are presented. Major backgrounds and methods of identifying
and dealing with them are indicated.Comment: Talk at DSU workshop, ITP Beijing, Oct. 2011. 9 figures, 2 table
Status of the CRESST Dark Matter Search
The CRESST experiment aims for a detection of dark matter in the form of
WIMPs. These particles are expected to scatter elastically off the nuclei of a
target material, thereby depositing energy on the recoiling nucleus. CRESST
uses scintillating CaWO4 crystals as such a target. The energy deposited by an
interacting particle is primarily converted to phonons which are detected by
transition edge sensors. In addition, a small fraction of the interaction
energy is emitted from the crystals in the form of scintillation light which is
measured in coincidence with the phonon signal by a separate cryogenic light
detector for each target crystal. The ratio of light to phonon energy permits
the discrimination between the nuclear recoils expected from WIMPs and events
from radioactive backgrounds which primarily lead to electron recoils. CRESST
has shown the success of this method in a commissioning run in 2007 and, since
then, further investigated possibilities for an even better suppression of
backgrounds. Here, we report on a new class of background events observed in
the course of this work. The consequences of this observation are discussed and
we present the current status of the experiment.Comment: Proceedings of the 13th International Workshop on Low Temperature
Detectors, 4 pages, 3 figure
Composite CaWO4 Detectors for the CRESST-II Experiment
CRESST-II, standing for Cryogenic Rare Events Search with Superconducting
Thermometers phase II, is an experiment searching for Dark Matter. In the LNGS
facility in Gran Sasso, Italy, a cryogenic detector setup is operated in order
to detect WIMPs by elastic scattering off nuclei, generating phononic lattice
excitations and scintillation light. The thermometers used in the experiment
consist of a tungsten thin-film structure evaporated onto the CaWO4 absorber
crystal. The process of evaporation causes a decrease in the scintillation
light output. This, together with the need of a big-scale detector production
for the upcoming EURECA experiment lead to investigations for producing
thermometers on smaller crystals which are glued onto the absorber crystal. In
our Run 31 we tested composite detectors for the first time in the Gran Sasso
setup. They seem to produce higher light yields as hoped and could provide an
additional time based discrimination mechanism for low light yield clamp
events.Comment: Proceedings of the Thirteenth International Workshop on Low
Temperature Detectors 4 pages, 9 figure
Intraocular pressure and ocular pulse amplitude using dynamic contour tonometry and contact lens tonometry
BACKGROUND: The new Ocular Dynamic Contour Tonometer (DCT), investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland) allows simultaneous recording of intraocular pressure (IOP) and ocular pulse amplitude (OPA). It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens(®), a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland). METHODS: Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens(®), and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens(®). RESULTS: No difference (P = 0.09) was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg) and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +/- 4.03 mm Hg). The IOP values of SmartLens(® )(mean: 20.25 mm Hg, median: 19.00 mm Hg, SD: +/- 4.96 mm Hg) were significantly higher (P = 0.0008) both from Goldmann tonometry and DCT. The OPA values of the DCT (mean: 3.08 mm Hg, SD: +/- 0.92 mm Hg) were significantly lower (P = 0.0003) than those obtained by SmartLens(® )(mean: 3.92 mm Hg, SD: +/- 0.83 mm Hg). CONCLUSIONS: DCT was equivalent to Goldmann applanation tonometry in measurement of IOP in a small group of normal subjects. In contrast, SmartLens(® )(contact lens tonometry) gave IOP readings that were significantly higher compared with Goldmann applanation tonometer readings. Both devices, DCT and SmartLens(® )provide the measurement of OPA which could be helpful e.g. for the management of glaucoma
GROND - a 7-channel imager
We describe the construction of GROND, a 7-channel imager, primarily designed
for rapid observations of gamma-ray burst afterglows. It allows simultaneous
imaging in the Sloan g'r'i'z' and near-infrared bands. GROND was
commissioned at the MPI/ESO 2.2m telescope at La Silla (Chile) in April 2007,
and first results of its performance and calibration are presented.Comment: 25 pages, 21 figs, PASP (subm); version with full-resolution figures
at http://www.mpe.mpg.de/~jcg/GROND/grond_pasp.pd
Surveying uveitis specialists—a call for consensus
Thomas Brennan became disillusioned with popular law school rankings and so decided to survey 100 academics, judges, and lawyers on his own, asking them to rank a list of ten schools he provided. He used a composite index similar in structure, but different in content, to those used by main-stream surveyors, such as U.S. News & World Report. As expected, many of the big name schools—Harvard, Yale, Stanford—made it to the top of the list. Penn State, as Brennan recalled, “[Was] about in the middle of the pack. Maybe fifth among the 10 schools listed. ” There was one small problem, however. Penn State had no law school at the time. Brennan had included it to make a point: surveys are limited by both the quality of the questions asked and by how familiar respondents are with the subject being surveyed [1, 2]
The effectiveness of pharmacological agents for the treatment of uveitic macular oedema (UMO): a systematic review protocol
PRISMA-P 2015 checklist: recommended items to include in a systematic review protocol. a (PDF 153Â kb
Discrimination of Recoil Backgrounds in Scintillating Calorimeters
The alpha decay of \n{{}^{210}Po} is a dangerous background to rare event
searches. Here, we describe observations related to this alpha decay in the
Cryogenic Rare Event Search with Superconducting Thermometers (CRESST). We find
that lead nuclei show a scintillation light yield in our \n{CaWO_4} crystals
of relative to electrons of the same energy. We describe a
way to discriminate this source of nuclear recoil background by means of a
scintillating foil, and demonstrate its effectiveness. This leads to an
observable difference in the pulse shape of the light detector, which can be
used to tag these events. Differences in pulse shape of the phonon detector
between lead and electron recoils are also extracted, opening the window to
future additional background suppression techniques based on pulse shape
discrimination in such experiments.Comment: 5 pages, 9 figure
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