A ug 2 00 5 Direct dark matter detection by observing electrons produced in neutralino - nucleus collisions

Exotic dark matter and dark energy together seem to dominate in the Universe. Supersymmetry naturally provides a candidate for the dark matter constituents via the lightest supersymmetric particle (LSP). The most important process for directly detecting dark matter is the LSP-nucleus elastic scattering by measuring the energy of the recoiling nucleus. In the present work we explore a novel process, which has definite experimental advantages, that is the detection of the dark matter constituents by observing the low energy ionization electrons. These electrons, which are produced during the LSP-nucleus collision, may be observed separately or in coincidence with the recoiling nuclei. We develop the formalism and apply it in calculating the ratio of the ionization rate to the nuclear recoil rate in a variety of atoms including 20Ne, 40Ar, 76Ge, 78Kr and 132Xe employing realistic Hartree-Fock e-mail: moustaki@ auth.gr e-mail: Vergados@ cc.uoi.gr e-mail: ejiri@ rcnp.osaka-u.ac.jp