From New Scientist:
[The] [f]irst results from the Large Underground Xenon (LUX) detector in South Dakota, announced today, failed to confirm previous potential sightings reported by other detectors. That may spell trouble for elegant recent theories of a shadow universe where myriad particles interact via their own dark forces.
Dark matter is the invisible stuff thought to make up about 80 per cent of the universe's matter, and that gives away its presence only by exerting a gravitational tug on ordinary matter. The most popular dark matter candidates are weakly interacting massive particles (WIMPs). So far unseen, these would also interact with normal matter via the weak force, so should smack into it every so often in a way that can be detected.
WIMP detectors are usually placed underground to shield them from background particles. Earlier this year, two such instruments in a Minnesota mine reported hints of WIMPs with a mass of between 1 and 10 gigaelectronvolts. The results back up intriguing models which say dark matter could be akin to normal matter in that it could be made of many kinds of particles, including low-mass WIMPs.