A third experiment has detected tantalising signs of dark matter. The finding raises more questions than answers, however, as two other experiments have found no sign of the mysterious stuff, which is thought to create the gravity that holds spinning galaxies together, accounting for about 85 per cent of all matter in the universe.
The new result comes from an experiment called CRESST II, which uses a few dozen supercooled calcium tungstate crystals to hunt for dark matter from deep beneath the Gran Sasso mountain in Italy. When a particle hits one of the crystals, the crystal gives off a pulse of light, and sensitive thermometers gauge the energy of the collision.
The vast majority of hits come from garden-variety particles such as cosmic rays. These rain down on Earth from space in such large numbers that they strike CRESST II – which is shielded by a kilometre of rock – at a rate of about one per second. This shield should have little effect on dark-matter particles because they are thought to interact very weakly with normal matter.
Now researchers led by Franz Pröbst and Jens Schmaler of the Max Planck Institute for Physics in Munich, Germany, say the experiment detected around 20 collisions between June 2009 and last April that may not have been caused by known particles.
The collisions may have involved dark matter, says team member Federica Petricca, also of the Max Planck Institute. She reported the results yesterday at the Topics in Astroparticle and Underground Physics conference in Munich.
To read the rest of the article, click here.