Cosmic-ray positrons from annihilation of weakly interacting massive particles in the galaxy

Allan J. Tylka
1989 Physical Review Letters  
The production of cosmic-ray positrons from the annihilation of weakly interacting massive particles (WIMP s) is considered. Conventional supersymmetric-neutralino annihilation generally yields an unobservably small e+ flux. However, a massive WIMP ()20 GeV) with a large annihilation cross section into a single e+e pair produces a distinctive and observable shelf in the cosmic-ray e+ spectrum. Only Dirac neutrinos obviously generate such a feature, but it may also appear in more elaborate
more » ... ore elaborate neutralino models. Such models are constrained by upper limits on the low-energy antiproton Aux. PACS numbers: 98.60.Ce, 14.80.Ly, 98.80.Cq One of the most important questions in astrophysics is the nature of the dark matter which apparently comprises galactic halos and may account for more than 90% of the mass of the Universe. ' Several lines of argument suggest that this dark matter is not baryonic and may therefore be in the form of exotic particle species surviving from the early Universe. Particle theory has provided many dark-matter candidates, among which are weakly interacting massive particles (WIMP's, hereafter referred to as g particles). A particularly interesting class of WIMP's consists of the supersymmetric neutralinos, which may be photinos (y), Higgsinos (h), or mixed states containing these. For a broad range of supersymmetry parameters, a cosmologically significant number of g particles should exist today. These g particles would have been incorporated into galactic halos, where they occasionally annihilate. The final states thus produced are quark-antiquark pairs, which then fragment into jets of hadrons, and lepton-antilepton pairs. Protons and antiprotons, y rays, electrons and positrons, and various neutrinos and antineutrinos remain after the decay of unstable particles. The cosmic P, y; e+, and v spectra may thus contain signatures of gg annihilation.
doi:10.1103/physrevlett.63.840 pmid:10041199 fatcat:6ltz3thrb5bvll62fkc3mf7wry