International Particle of Mystery

The ­generic line on dark matter is that nobody knows what it is because nobody has seen it. The former claim remains unassailable—any number of hypothetical particles could be dark matter. As to whether or not anybody has seen it, scientists are as divided as ever, and the discourse among rival dark matter hunters is getting chippy. The controversy centers on an Italy-based research group that runs DAMA, a particle detector that the researchers have claimed for years is picking up dark matter particles. But the group has been secretive about its data, critics say, and physicists have by and large remained skeptical. Indeed, in April a top experimental collab­oration known as XENON100 reported findings that appeared to rule out the possibility that DAMA’s signal came from dark matter.   link