Lightest Supersymmetric Particle

The lightest supersymmetric particle (English lightest supersymmetric particle, LSP for short ) is the hypothetical lightest elementary particles in supersymmetry.

Properties

The CSP has the characteristic of supersymmetric particles R- parity. In model theory, in which the R- parity is preserved in interaction processes, it therefore has the following properties:

  • This particle must be absolutely stable. The reason is that there is no lighter supersymmetric particles, in which could disintegrate it, and because of the R- parity conservation is only a decay into ordinary matter excluded ( with R- parity 1).
  • Any other supersymmetric particles must sooner or later fall into an odd number of LSP,
  • In particle accelerators, it will ( if at all) can only produce an even number.

WIMP candidate

The CSP is a much-discussed candidate for the dark matter forming WIMP ( weakly interacting massive particles).

It is considered unlikely that the LSP participates in the electromagnetic or strong interaction ( as carriers of color charge ). Otherwise, it would have been condensed during the matter - formation in the early universe with ordinary matter and already discovered because of its large mass.

For example, there are tight experimental limits on the frequency of heavy isotopes. Norman and co-authors (1987 ) give an upper limit of the frequency of such negatively charged " super heavy " isotopes of 1.2 · 10-12 per nucleon. of. For the relative abundance of the LSPs compared to the frequency of the proton is given by Ellis and Flores ( 1988) for the mass range of LSPs 1-107 GeV / c ², an upper limit of 10-15 to 10-30. If you participate in the strong interaction, one would expect, but values ​​of 10-10 and participation in the electromagnetic interaction of 10-6.

As WIMP candidates the following hypothetical supersymmetric particles remain:

Sneutrino

The sneutrino of the ordinary MSSM is the super partner of the ( normal, left-handed ) neutrinos. It differs according to previous experiments of (Z - boson decay width at LEP ).

In the form of sterile Sneutrinos ( superpartners of the right-handed neutrinos or sterile ) but it is still being debated in some extended models as a possibility.

Gravitino and NSP

Gravitinos as LSP lead to cosmological problems: their interaction with ordinary matter is too weak to be eligible for the observed thermally produced in the early universe dark matter in question.

However, it is possible that gravitinos are the final decay product of that time produced other supersymmetric particles. The search would then apply these NSPs also hypothetical or NLSPs ( lightest supersymmetric particles next to, second - lightest supersymmetric particle ).

Neutralino

As a favorite candidate is currently the lightest neutralino (also referred to as ), ie a mixture of different superpartners of neutral gauge bosons ( gauginos thus, more Bino and Wino0 ) and Super partners also neutral Higgs boson (ie Higgsinos ). The Particle Data Group announced in 2006 as an experimental lower limit on the neutralino mass 46 GeV / c ² to; for comparison, the mass of the proton is 0.94 GeV / c ².

Hypothesis Electromagnetism Minimal Supersymmetric Standard Model Large Electron–Positron Collider Sterile neutrino John Ellis (physicist)
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