A New WIMP Population in the Solar System and New Signals for Dark-Matter Detectors

Abstract

We describe in detail how perturbations due to the planets can cause a sub-population of WIMPs captured by scattering in surface layers of the Sun to evolve to have orbits which no longer intersect the Sun. We argue that such WIMPs, if their orbit has a semi-major axis less than 1/2 of Jupiter's, can persist in the solar system for cosmological timescales. This leads to a new, previously unanticipated WIMP population intersecting the Earth's orbit. The WIMP-nucleon cross sections required for this population to be significant are precisely those in the range predicted for SUSY dark matter, lying near the present limits obtained by direct underground dark matter searches using cyrogenic detectors. Thus, if a WIMP signal is observed in the next generation of detectors, a potentially measurable signal due to this new population must exist. This signal, lying in the keV range for Germanium detectors, would be complementary to that of galactic halo WIMPs. A comparison of event rates, anisotropies, and annual modulations would not only yield additional confirmation that any claimed signal is indeed WIMP-based, but would also allow one to gain information on the nature of the underlying dark matter model.