Direct Wimp Detection in Directional Experiments

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Thus the direct dark matter search, consisting of detecting the recoiling nucleus, is central to particle physics and cosmology. Modern particle theories naturally provide viable cold dark matter candidates with masses in the GeV-TeV region. Supersymmetry provides the lightest supersymmetric particle (LSP), theories in extra dimensions the lightest Kaluza-Klein particle (LKP) etc. In such theories the expected rates are much lower than the present experimental goals. So one should exploit characteristic signatures of the reaction, such as the modulation effect and, in directional experiments, the correlation of the event rates with the sun's motion. In standard non directional experiments the modulation is small, less than two per cent and the location of the maximum depends on the unknown particle's mass. In directional experiments, in addition to the forward-backward asymmetry due to the sun's motion, one expects a larger modulation, which depends on the direction of observation. We study such effects both in the case of a light and a heavy target. Furthermore, since it now appears that the planned experiments will be partly directional, in the sense that they can only detect the line of the recoiling nucleus, but not the sense of direction on it, we study which of the above mentioned interesting features, if any, will persist in these less ambitious experiments.Comment: 22 LaTex pages, 28 figure

Some issues related to the direct detection of dark matter

We briefly review some theoretical issues involved in the direct detection of supersymmetric (SUSY) dark matter. After a brief discussion of the allowed SYSY parameter space we focus on the determination of the traditional neutralino detection rates, in experiments which measure the energy of the recoiling nucleus, such as the coherent and spin induced rates and the dependence of the rate on the motion of the Earth (modulation effect). Then we examine the novel features appearing in directional experiments, which detect the recoiling nucleus in a given direction. Next we estimate the branching ratios for transitions to accessible excited nuclear levels. Finally we estimate the event rates leading to the atom ionization and subsequent detection of the outgoing electrons.Comment: LaTex, 15 pages, 3 PostScript figure