Cold dark matter candidates and the solar neutrino problem

Certain currently proposed weakly interacting elementary particles can have a high probability of solar capture if they make up the Galactic halo. Their present abundance in the sun is here determined by balancing capture rates against annihilation rates. Both particle physics and cosmological considerations impose constraints on scattering and annihilation cross sections. In general, for the candidate particles here discussed (massive neutrinos, supersymmetric scalar neutrinos, and photinos), the inferred solar abundances are too small by three to four orders of magnitude to solve the solar neutrino problem. Extreme fine tuning, marginally possible in the case of the photino, could increase solar abundances to a level where the neutrino signature would be affected. Otherwise, either a particle with a net cosmological asymmetry, or else a new mechanism for strengthening the existing Majorana suppression of s-wave annihilation at very low energies, would seem to be required.