Non-baryonic dark matter: observational evidence and detection methods

Abstract

The evidence for the existence of dark matter in the universe is reviewed. A\ngeneral picture emerges, where both baryonic and non-baryonic dark matter is\nneeded to explain current observations. In particular, a wealth of\nobservational information points to the existence of a non-baryonic component,\ncontributing between around 20 and 40 percent of the critical mass density\nneeded to make the universe geometrically flat on large scales. In addition, an\neven larger contribution from vacuum energy (or cosmological constant) is\nindicated by recent observations. To the theoretically favoured particle\ncandidates for non-baryonic dark matter belong axions, supersymmetric\nparticles, and of less importance, massive neutrinos. The theoretical\nfoundation and experimental situation for each of these is reviewed. Direct and\nindirect methods for detection of supersymmetric dark matter are described in\nsome detail. Present experiments are just reaching the required sensitivity to\ndiscover or rule out some of these candidates, and major improvements are\nplanned over the coming years.\n