Dark Matter Research
In recent years cosmologicl observations have provided increasingly convincing evidence that non-baryonic dark matter is the building block of all structures in the Universe. Galactic dark matter was suggested to solve the discrepancy between observed (luminous) matter in the Universe and that inferred by dynamical considerations. A matter density of about 30% of the critical density of the universe can be composed of dark matter. The mystery of the dark matter in the universe remains unsolved. Among the most plausible candidates are weakly interacting massive particles (WIMP), of which the supersimmetric neutralino is a favourite candidate from the point of view of particle physics. The neutralino arises naturally in supersymmetric extension of the standard model, and has the attractive feature of giving a relic density which in large region of parameter space is adequate to explain cosmological dark matter. |
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Neutralino are Majorana fermions and will annihilate with each other in the halo, resulting in the symmetric production of particles and antiparticles, the latter providing an observable signature.
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Annihilations |
Some models predict that the antiproton flux at energies of tens of GeV resulting from annihilation of high-mass neutralinos (e.g. Higgsinos) could be more than an order of magnitude above the flux of secondary antiprotons, and thus could be unambiguously observed. The most interesting energy range of this search should be above ~10 GeV, where the excellent performances of Pamela are combined with the smallness of the solar modulation effects. |
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Antiproton |
WIMPs could contribuite to the positron flux by direct annihilation in e+e-, and to continuum positrons from the other annihilation channels. This could be seen as an excess or bump beginning at a few GeV and extending upward in energy to a point depending on the WIMP mass. |
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Positrons |