| Edelweiss | |
|---|---|
 |
|
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Tribe: | Gnaphalieae[1] |
| Genus: | Leontopodium |
| Species: | L. alpinum |
| Binomial name | |
| Leontopodium alpinum Cass., 1822 |
|
Edelweiss (pronounced /ˈedəlvaɪs/; Leontopodium alpinum), is one of the best-known European mountain flowers, belonging to the sunflower family (Asteraceae). The name comes from German edel (meaning noble) and weiss (meaning white). The scientific name, Leontopodium, means "lion's paw" and is derived from the Greek words leon (lion) and podion (diminutive of pous, foot).
Leaves and flowers are covered with white hairs and appear woolly (tomentose). Flowering stalks of Edelweiss can grow to a size of 3–20 cm (in cultivation, up to 40 cm). Each bloom consisting of five to six small yellow flower heads (5 mm) surrounded by leaflets in star form. The flowers are in bloom between July and September.
The plant is unequally distributed and prefers rocky limestone places at 2000–2900 m altitude. It is not toxic, and has been used traditionally in folk medicine as a remedy against abdominal and respiratory diseases. The dense hair appears to be an adaptation to high altitudes, protecting the plant from cold, aridity and UV radiation.[2] Since it usually grows in inaccessible places, it is associated in many countries of the alpine region with mountaineering. Its white colour is considered a symbol of purity, and holds a Latin as well as Romanian name, floarea reginei (Queen's flower).
Edelweiss is a protected plant in many countries, including Mongolia, Bulgaria, Croatia, Switzerland, France, Norway, Italy, Malaysia (In Genting and Cameron Highlands), Indonesia (In Semeru Mountain), Germany, Spain (Ordesa National Park), Poland and Slovakia (Tatra National Park), Slovenia (in Gorizia and Gradisca since 1896, in Carniola since 1898), Austria (since 1886) and Romania (since 1933).
Leontopodium alpinum is grown in gardens for its interesting inflorescence and silver foliage,[3] the plants are short lived and can be grown from seed.[4]
EDELWEISS (Expérience pour DEtecter Les Wimps En Site Souterrain) is a dark matter search experiment located in the Modane Underground Laboratory. 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.
Contents |
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 signficant 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).
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 ~20mK temperature. 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.
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 problem, the collaboration have 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. This allows >99.5% of surface events to be rejected[1].
The results from the first phase of the experiment (EDELWEISS I) have been published, excluding WIMP dark matter with an interaction cross-section above ~10-6pb[2]. The current phase - EDELWEISS II – is now taking data. The experiment will run through 2010, after which the EURECA experiment plans to start construction in the Modane laboratory.
EDELWEISS is a collaboration of the following member institutions:
EDELWEISS, known botanically as Leontopodium alpinum, a member of the family Compositae, a native of the Alps of Central Europe. It is a small herb reaching about 6 in. high, with narrow white woolly leaves, and terminal flower-heads enveloped in woolly bracts. The woolly covering enables the plant to thrive in the exposed situations in which it is found, by protecting it from cold and from drying up through excessive loss of moisture. It is grown in Britain as a rockplant.
   | Edelweiss - Hribi.net - Edelweiss (Leontopodium alpinum) |
| | doi:10.1103/PhysRevD.71.122002 - Phys. Rev. D 71 (2005): V. Sanglard et al. EDELWEISS Collaboration - Final results of the... |
| | doi: 10.1007/s10909-9742-5 - DOI Not Found |
| | astro-ph/0503265 - [astro-ph/0503265] Final results of the EDELWEISS-I dark matter search with cryogenic heat-and-ionization Ge detectors |
|
|
Wikis
Quiz
Misc
Search
![[1]](http://www.aldaver.com/Images/Owb/14/lg2014sz.gif){kind=link}