CANDIDATE DARK MATTER PARTICLES, specifically thought to be examples of "weakly interacting massive particles" (WIMPs), have been indirectly detected by a group operating in the Gran Sasso National Lab (INFN) in Italy, according to a paper to be delivered by Pierluigi Belli of the University of Rome (DAMA collaboration) at a dark matter detection meeting in Marina del Rey, California this week (a meeting sponsored by UCLA: information from dm20@physics.ucla.edu).

Dark matter is a hypothetical non-luminous substance thought to be lurking in and around galaxies, influencing the way the galaxies rotate and interact. The dark matter might consist in part of baryons (particles such as the protons found in common atoms) or more novel forms such as WIMPs. Because of the way the Earth orbits the sun and the way our solar system moves through the galaxy (buffeting the presumed dark matter halo as it goes) there is reason to think that the flux of WIMP wind we encounter (and the rate at which WIMPs feebly interact in terrestrial detectors) would be higher in June than in December.

The DAMA experiment reports having discovered just such an seasonal effect in the frequency of events in which a presumed incoming WIMP (with masses about 50 times that of the proton) strikes a shielded sodium-iodine scintillation material, causing tiny flashes of light deep within the detector (INFN preprint AE-00/01; www.lngs.infn.it). Dark matter interactions in detectors are expected to be rare and analysis difficult, so the DAMA interpretation will be subject to great scrutiny at the California meeting, where other groups searching for WIMPs will be reporting as well.