11 research outputs found
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes
The EDELWEISS-II collaboration has completed a direct search for WIMP dark
matter with an array of ten 400-g cryogenic germanium detectors in operation at
the Laboratoire Souterrain de Modane. The combined use of thermal phonon
sensors and charge collection electrodes with an interleaved geometry enables
the efficient rejection of gamma-induced radioactivity as well as near-surface
interactions. A total effective exposure of 384 kg.d has been achieved, mostly
coming from fourteen months of continuous operation. Five nuclear recoil
candidates are observed above 20 keV, while the estimated background is 3.0
events. The result is interpreted in terms of limits on the cross-section of
spin-independent interactions of WIMPs and nucleons. A cross-section of
4.4x10^-8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints
are also set on models where the WIMP-nucleon scattering is inelastic.Comment: 23 pages, 5 figures; matches published versio
A detection system to measure muon-induced neutrons for direct Dark Matter searches
International audienceMuon-induced neutrons constitute a prominent background component in a number of low count rate experiments, namely direct searches for Dark Matter. In this work we describe a neutron detector to measure this background in an underground laboratory, the Laboratoire Souterrain de Modane. The system is based on 1 m of Gd-loaded scintillator and it is linked with the muon veto of the EDELWEISS-II experiment for coincident muon detection. The system was installed in autumn 2008 and passed since then a number of commissioning tests proving its full functionality. The data-taking is continuously ongoing and a count rate of the order of 1 muon-induced neutron per day has been achieved
A new high-background-rejection dark matter Ge cryogenic detector
A new design of a cryogenic germanium detector for dark matter search is
presented, taking advantage of the coplanar grid technique of event
localisation for improved background discrimination. Experiments performed with
prototype devices in the EDELWEISS II setup at the Modane underground facility
demonstrate the remarkably high efficiency of these devices for the rejection
of low-energy , approaching 10 . This opens the road to investigate
the range beyond 10 pb in the WIMP-nucleon collision cross-sections, as
proposed in the EURECA project of a one-ton cryogenic detector mass.Comment: submitted to Physical Review Letter
Combined Limits on WIMPs from the CDMS and EDELWEISS Experiments
The CDMS and EDELWEISS collaborations have combined the results of their
direct searches for dark matter using cryogenic germanium detectors. The total
data set represents 614 kg.d equivalent exposure. A straightforward method of
combination was chosen for its simplicity before data were exchanged between
experiments. The results are interpreted in terms of limits on spin-independent
WIMP-nucleon cross-section. For a WIMP mass of 90 GeV/c^2, where this analysis
is most sensitive, a cross-section of 3.3 x 10^{-44} cm^2 is excluded at 90%
CL. At higher WIMP masses, the combination improves the individual limits, by a
factor 1.6 above 700 GeV/c^2. Alternative methods of combining the data provide
stronger constraints for some ranges of WIMP masses and weaker constraints for
others.Comment: Events, efficiencies, and main limit are available in text format
(see README.txt
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes
The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4×10-8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic. © 2011 Elsevier B.V
Full Inter-Digitized Detectors For The EDELWEISS-II Dark Matter Search
International audienceA new design for the Ge bolometers of the EDELWEISS project is described here, based on innovative interleaved charge collection electrodes with high background discrimination capabilities. The measured surface event rejection is compatible with WIMP sensitivity levels down to 10(-) 9 picobarn (pb). Use of interleaved electrodes on the overall surface of the Ge crystal, including its lateral surface, results to a high fiducial volume of the order of 80%. Electronic setup is fairly simple with a total of five JFET based read-out amplifiers, one for the NTD-Ge heat channel and four for the ionization signal. Fabrication process is quite simple and the design is easily scalable to higher mass bolometers (1 kg Ge crystal), making it very appealing for the future 1 ton scale EUREKA Dark Matter experiment
First results of the EDELWEISS-II WIMP search using Ge cryogenic detectors with interleaved electrodes
14 pages, 3 figures. Submitted to Phys Lett. BThe EDELWEISS-II collaboration has performed a direct search for WIMP dark matter with an array of ten 400 g heat-and-ionization cryogenic detectors equipped with interleaved electrodes for the rejection of near-surface events. Six months of continuous operation at the Laboratoire Souterrain de Modane have been achieved. The observation of one nuclear recoil candidate above 20 keV in an effective exposure of 144 kgd is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 1.0x10^-7 pb is excluded at 90%CL for a WIMP mass of 80 GeV/c2. This result demonstrates for the first time the very high background rejection capabilities of these simple and robust detectors in an actual WIMP search experiment
Monitoring of the thermal neutron flux in the LSM underground laboratory
submitted to Journal of Physics G: Nuclear and Particle Physics, 8 pages, 4 figuresThis paper describes precise measurements of the thermal neutron flux in the LSM underground laboratory in proximity of the EDELWEISS-II dark matter search experiment together with short measurements at various other locations. Monitoring of the flux of thermal neutrons is accomplished using a mobile detection system with low background proportional counter filled with He. On average 75 neutrons per day are detected with a background level below 1 count per day (cpd). This provides a unique possibility of a day by day study of variations of the neutron field in a deep underground site. The measured average 4 neutron flux per cm in the proximity of EDELWEISS-II is neutrons/sec. We report the first experimental observation that the point-to-point thermal neutron flux at LSM varies by more than a factor two