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EDELWEISS ( Expérience pour DEtecter Les WIMPs En Site Souterrain) is a dark matter search experiment located at the Modane Underground Laboratory in France. The experiment uses cryogenic detectors, measuring both the phonon and ionization signals produced by particle interactions in germanium crystals. This technique allows nuclear recoils events to be distinguished from electron recoil events.

The EURECA project is a proposed future dark matter experiment, which will involve researchers from EDELWEISS and the CRESST dark matter search.

Dark matter
Main article: dark matter

Dark matter is material which does not emit or absorb light. Measurements of the rotation curves of spiral galaxies suggest it makes up the majority of the mass of galaxies; and precision measurements of the cosmic microwave background radiation suggest it accounts for a significant fraction of the density of the Universe.

A possible explanation of dark matter comes from particle physics. WIMP (Weakly Interacting Massive Particle) is a general term for hypothetical particles which interact only through the weak nuclear and gravitational force. This theory suggests our galaxy is surrounded by a dark halo of such particles. EDELWEISS is one of a number of dark matter search experiments aiming to directly detect WIMP dark matter, by detecting the elastic scattering of a WIMP off an atom within a particle detector. As the interaction rate is so low, this requires sensitive detectors, good background discrimination, and a deep underground site (to reduce the background from cosmic rays).
Experiment

EDELWEISS is located in the Modane underground laboratory, in the Fréjus road tunnel between France and Italy, below 1800m of rock. A 20 cm lead shield reduces the gamma background, and a polyethylene shield reduces the neutron flux. All materials close to the detectors are screened for radiopurity. A dilution refrigerator is used to cool the detectors, built in the opposite orientation to most instruments with the detectors at the top and the refrigeration mechanism below.

EDELWEISS uses high purity germanium cryogenic bolometers cooled to 20 milliKelvin above absolute zero. The phonon and ionization signals produced by a particle interaction are measured. This allows background events to be rejected as nuclear recoils events (produced by WIMP or neutron interactions) produce much less ionization than electron recoil events (produced by alpha, beta and gamma radiation). The detectors are similar to those used by the CDMS experiment. Simultaneous detection of ionization and heat with semiconductors at low temperature was an original idea by Lawrence M. Krauss, Mark Srednicki and Frank Wilczek.[1]

A major limitation of early detectors was the problem of surface events. Due to incomplete charge collection, a particle interaction near the surface of the crystal gave no ionization signal, so electron recoils near the surface could be mistaken for nuclear recoils. To avoid this, the collaboration developed new detectors with interdigitised electrodes. Different voltages are applied to a series of electrodes so the direction of electric field is different near the surface of the crystal, allowing over 99.5% of surface events to be rejected.[2]
Results
Fig A. EDELWEISS I results. With CDMS parameter space excluded as of 2004. DAMA result is located in green area and is disallowed.

The results from the first phase of the experiment (EDELWEISS I) were published in 2005, excluding WIMP dark matter with an interaction cross-section above ≈10−6 pb (at ≈85 GeV).[3]:Fig 15

EDELWEISS-II ran 2009–10 with 10 detectors, that is, 4 kg of detector mass (for a total effective exposure of 384 kg·d)[4] limiting high mass[4]:Fig 5 and low mass WIMPs,[5] and axions.[6] A cross-section of 4.4×10−8 pb is excluded at 90% C.L. for WIMP mass of 85 GeV. (Just above projected CDMS results in Fig A.)

EDELWEISS-III had 40 detectors.[6] EDELWEISS-III conducted first science run 2014-2015 with results published in 2016.

EURECA design work will continue for operation after the EDELWEISS-III run. It is planned that EURECA would start operating after 2017.
Collaboration

EDELWEISS is a collaboration of the following member institutions:
CEA – Commissariat à l'Énergie Atomique

IRFU - Institut de Recherche sur les Lois Fondamentales de l'Univers
IRAMIS - Institut Rayonnement Matière de Saclay

CNRS – Centre National de la Recherche Scientifique

CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay
IPNL - Institut de Physique Nucléaire de Lyon
Institut NÉEL, Grenoble
IAS - Institut d'Astrophysique Spatiale, Paris

Institutions outside France

Universität Karlsruhe, Germany
Forschungszentrum Karlsruhe, Germany
JINR – Joint Institute for Nuclear Research, Dubna, Russia
University of Oxford

References

Krauss, L.; Srednicki, M.; Wilczek, F. (1986). "Solar System Constraints and Signatures for Dark Matter Candidates". Physical Review D. 33 (8): 2079–2083. Bibcode:1986PhRvD..33.2079K. doi:10.1103/PhysRevD.33.2079.
Juillard, A. (2008). "Status of the EDELWEISS-II Experiment". Journal of Low Temperature Physics. 151 (3–4): 806–811. Bibcode:2008JLTP..151..806J. doi:10.1007/s10909-008-9742-5.
Sanglard, V.; et al. (EDELWEISS Collaboration) (2005). "Final results of the EDELWEISS-I dark matter search with cryogenic heat-and-ionization Ge detectors". Physical Review D. 71 (12): 122002.arXiv:astro-ph/0503265. Bibcode:2005PhRvD..71l2002S. doi:10.1103/PhysRevD.71.122002.
Armengaud, E.; et al. (EDELWEISS Collaboration) (2011). "Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes". Physics Letters B. 702 (5): 329–335.arXiv:1103.4070. Bibcode:2011PhLB..702..329E. doi:10.1016/j.physletb.2011.07.034.
Armengaud, E.; et al. (EDELWEISS Collaboration) (2012). "A search for low-mass WIMPs with EDELWEISS-II heat-and-ionization detectors". Physical Review D. 86 (5): 051701.arXiv:1207.1815. Bibcode:2012PhRvD..86e1701A. doi:10.1103/PhysRevD.86.051701.

Armengaud, E.; et al. (EDELWEISS Collaboration) (2013). "Axion searches with the EDELWEISS-II experiment". Journal of Cosmology and Astroparticle Physics. 2013 (11): 067.arXiv:1307.1488. Bibcode:2013JCAP...11..067A. doi:10.1088/1475-7516/2013/11/067.

External links

EDELWEISS Collaboration home page
EURECA Collaboration home page

vte

Dark matter
Forms of
dark matter

Baryonic dark matter Cold dark matter Hot dark matter Light dark matter Mixed dark matter Warm dark matter Self-interacting dark matter Scalar field dark matter Primordial black holes


Hypothetical particles

Axino Axion Dark photon Holeum LSP Minicharged particle Neutralino Sterile neutrino SIMP WIMP

Theories
and objects

Cuspy halo problem Dark fluid Dark galaxy Dark globular cluster Dark matter halo Dark radiation Dark star Dwarf galaxy problem Halo mass function Mass dimension one fermions Massive compact halo object Mirror matter Navarro–Frenk–White profile Scalar field dark matter

Search
experiments
Direct
detection

ADMX ANAIS ArDM CDEX CDMS CLEAN CoGeNT COSINE COUPP CRESST CUORE D3 DAMA/LIBRA DAMA/NaI DAMIC DarkSide DARWIN DEAP DM-Ice DMTPC DRIFT EDELWEISS EURECA KIMS LUX LZ MACRO MIMAC NAIAD NEWAGE NEWS-G PandaX PICASSO PICO ROSEBUD SABRE SIMPLE TREX-DM UKDMC WARP XENON XMASS ZEPLIN

Indirect
detection

AMS-02 ANTARES ATIC CALET CAST DAMPE Fermi HAWC HESS IceCube MAGIC MOA OGLE PAMELA VERITAS

Other projects

MultiDark PVLAS

Potential dark galaxies

HE0450-2958 HVC 127-41-330 Smith's Cloud VIRGOHI21

Related

Antimatter Dark energy Exotic matter Galaxy formation and evolution Illustris project Imaginary mass Negative mass UniverseMachine

Physics Encyclopedia

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Index

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