Weakly interacting massive particles

WIMP (of English Weakly Interacting Massive Particles, German weakly interacting massive particles, pun engl wimp. , Weakling ') are hypothetical particles of particle physics with a mass between a few tens and a thousand GeV / c ² ( a GeV / c ², a billion eV divided by the square of the velocity of light c is about the mass of a hydrogen atom ). WIMPs have been postulated to solve the cosmological problem of dark matter in space.

The existence of dark matter was postulated because gravity existing in the universe visible matter would not be nearly enough to explain the clumping of matter in the early stage of the cosmos, which led to the formation of galaxies. The bulk of the matter contained in the universe must therefore be composed of not directly visible " dark matter ", although it is not clear what is to be imagined below.

The existence of dark matter can be explained by heavy ( mass of about two gold atoms), only the weak interaction and gravitation unsuccessful WIMPs that traverse the space in large numbers. They have no charge and hence no electric or magnetic field, so that its interaction with matter is limited to gravity and the very short-range weak interaction. Since WIMPs, if they actually exist, are not subject to the strong interaction, therefore, they could as neutrinos whole planets traverse completely undisturbed. The English word " wimp " in German means something like " weakling ", which alludes to this inability to influence matter, and is also to be understood as opposed to the MACHOs, which have also been proposed as a hypothesis for the dark matter.

Experiments

The experimental detection of WIMPs is the subject of current research. Because of the extremely rare interaction with any matter you attempted to detect WIMPs indirectly through decays. In extremely rare cases, it must happen that a WIMP collides directly with a nucleus, which would thereby also radiate. To detect this radiation requires special detectors that not only measure the radiation, but they can also differ from the interfering background radiation.

The currently most sensitive experiments using cryogenic detectors ( detectors that operate at very low temperatures ). These include:

• The American experiment CDMS -II ( Cryogenic Dark Matter Search ) in the Soudan Underground Laboratory,
• The Franco- German EDELWEISS experiment (Experience pour DETECTER Les Wimps En Site Souterrain ) in the Laboratoire Souterrain de Modane,
• XENON Dark Matter Project at the Gran Sasso underground laboratory
• The German -British experiment CRESST ( Cryogenic Rare Event Search with Superconducting Thermometers ) in the Laboratori nazionali del Gran Sasso and

DAMA 2007 delivered with a pre undoubted result of many: the experimenters claim to have observed a signal of WIMPs with a large detector of sodium iodide ( NaI ). This result is difficult to reconcile with the results of other experiments and the theoretical expectations.

Super - WIMPs

An advanced concept provides so-called super - WIMPs caused by the decay of WIMPs. They have an even weaker interaction than WIMPs, since they interact only with gravity, but not with the weak nuclear force.

The existence of super- WIMPs would affect the formation of galaxies. Super - WIMPs would have moved in the early universe very quickly. Only after they had come to rest, have galaxies can form. This means that the matter would have had less time to compress in the center of galaxies, which would have had an effect on the density in the center of dark matter halos. In this way could prove to you whether these halos are made of WIMPs or super - WIMPs.

Another proof of possibility could arise from the decay of WIMPs in Super WIMPs themselves, as this photons and electrons might arise, the light nuclei would break when they met on this. Evidence that the universe contains less lithium than expected, could thus be explained.

Alternative theories of dark matter

Axions

Another particle that has been proposed to solve the problem of dark matter is the axion. This also hypothetical particles could be produced, among other stars. Through interaction with strong magnetic fields could be converted into a photon whose energy corresponds to that of the axions. Axions from the sun should generate photons with frequencies in the range of X-rays. The CAST experiment at CERN has been paid to detect this particle with a 9 -Tesla magnet.

MACHO

Conjectures in the dark matter if it were massive, but cold and not radiant celestial bodies that are present in large numbers in the galaxies ( MACHOs ), could not be confirmed by research.

Dark Forces

After Jonathan Feng of the University of California at Irvine, and Jason Kumar of the University of Hawaii at Manoa supersymmetry also allows for alternative concepts without WIMPs, with several other types of particles. Many of these concepts are also of the existence of "dark forces " of, hidden versions of the weak and the electromagnetic force. The existence of a dark electromagnetism would cause the dark matter would be able to send out hidden light and reflect. Even if such a light and the dark forces remained hidden from us, but they could affect. Clouds of dark particles that penetrate each other, would be distorted, which could have an impact on objects such as galaxy clusters. Similar studies on Bullet Cluster have shown that this effect, at least can not be very strong. The dark forces, if they exist, that are only weakly.

Another effect would result from the fact that dark forces would allow the dark matter particles exchanging energy and momentum. Dark matter halos, which would have been wrong initially, would be spherical over time, which in turn impact on galaxies would, in particular dwarf galaxies. Dark Matter in their surroundings moves very slowly. This causes particles to each other to stay longer. Small effects therefore have more time to impact. The observation that small galaxies are consistently rounder than large, could help to explain what would be an indication for the existence of dark forces as a result.