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Edelweiss

Experiment for direct detection of dark matter
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Home page for the EDELWEISS experiment

The Edelweiss experiment is dedicated to the direct detection of dark matter particles with bolometric detectors located at the underground laboratory of Modane (the LSM). The results of the stage II of this experiment are published, while a third phase is in preparation. On this Web site you will find the following sections:

Contact: CEA / IN2P3

"Ge-ID" interleaved germanium bolometer Bolometer towers being installed The cryostat and shieldings

Summer 2012 - A search for low-mass WIMPs with EDELWEISS-II (arXiv:1207.1815)

We report on a search for low-energy (E < 20 keV) WIMP-induced nuclear recoils using data collected in 2009 - 2010 by EDELWEISS from four germanium detectors equipped with thermal sensors and an electrode design (ID) which allows to efficiently reject several sources of background. The data indicate no evidence for an exponential distribution of low-energy nuclear recoils that could be attributed to WIMP elastic scattering after an exposure of 113 kg.d. For WIMPs of mass 10 GeV, the observation of one event in the WIMP search region results in a 90% CL limit of 1.0x10^-5 pb on the spin-independent WIMP-nucleon scattering cross-section, which constrains the parameter space associated with the findings reported by the CoGeNT, DAMA and CRESST experiments.

March 2011 - Final results of the EDELWEISS-II WIMP search with Ge-ID detectors (arXiv:1103.4070)

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 less than 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. See also:

December 2009 - CDMS and Edelweiss results : status and what can be hoped for in 2010

The CDMS collaboration, from an effective exposure of 194 kg.d, has observed two events statistically consistent with an expected background of about one event for this experiment. While the presence of a signal is not excluded, this result calls for larger statistics, reduction of background level and assessment of background estimates to identify unambiguously a WIMP signal.

The EDELWEISS collaboration (gathering 60 collaborators, originating from France, Germany, Russia and United Kingdom), with a slightly lower effective exposure of 144 kg.d, has recently demonstrated (arXiv link) that its detectors have the qualities needed to explore the sensitivity domain reached by CDMS and significantly beyond. The presence of a single event just above 20 keV in the region of signal can be assigned, at the present stage of the analysis, to a WIMP signal or a background interaction.

EDELWEISS benefits from a deep underground laboratory, on the border between France and Italy, with a reduction in the cosmic-ray background reduced by a factor 30 relative to the Soudan site where the CDMS experiment is presently set.

The continuation of the present run should result in Spring 2010 in a doubling of the present sensitivity. In addition, an analysis of low energy region below 20 keV together with systematic studies to determine with precision the expected background will be performed and should bring more insight into this newly explored region of sensitivity.

By summer 2010, new detectors will be installed, which might allow to identify unambiguously a possible signal, or pursue a deeper exploration of even more elusive WIMPs.

December 2009 - First WIMP search with "Interdigit" detectors

A first WIMP search using 6 months of data taken with 10 ID bolometers was carried out. Results are presented on arXiv. They represent an improvment of more than an order of magnitude with respect to previous EDELWEISS-I results. Data taking are continuing in order to improve the statistics.

Spring 2009 - First results on "Interdigit" detectors

While a background physics data taking is going on with around ten Interdigit detectors, the performance of theses sensors, obtained during 2008 data takings, were published in Physics Letters B (link on arXiv).

Edelweiss-II: Press releases, podcasts...