Has dark matter finally been discovered?

Scientists claim they are closer than ever to piercing the mystery of dark matter - which is challenging conventional notions of the cosmos - and the first clues may be unveiled within two weeks.

The findings will be revealed in the results from the Alpha Magnetic Spectrometer (AMS), a particle collector mounted on the outside of the International Space Station (ISS), said Massachusetts Institute of Technology (MIT) physicist Samuel Ting, AMS principle investigator.

Though Ting did not say what exactly the experiment has found, he noted the results bear on the mystery of dark matter, the invisible type of matter hypothesised to account for a large part of the total mass in the universe, 'SPACE.com' reported.
"It will not be a minor paper," Ting said at the annual meeting of the American Association for the Advancement of Science here.

Hinting that the findings were important enough that the scientists rewrote the paper 30 times before they were satisfied with it, Ting said, it represents a "small step" in figuring out what dark matter is, and perhaps not the final answer.

Some physics theories suggest that dark matter is made of WIMPS (weakly interacting massive particles), a class of particles that are their own antimatter partner particles.
When matter and antimatter partners meet, they annihilate each other, so if two WIMPs collided, they would be destroyed, releasing a pair of daughter particles - an electron and its antimatter counterpart, the positron, in the process. The Alpha Magnetic Spectrometer has the potential to detect the positrons and electrons produced by dark matter annihilations in the Milky Way.

The USD 2 billion machine was installed on the ISS in May 2011, and so far, it has detected 25 billion particle events, including about 8 billion electrons and positrons.
This first science paper will report how many of each were found, and what their energies are, Ting said.

If the experiment detected an abundance of positrons peaking at a certain energy, that could indicate a detection of dark matter, because while electrons are abundant in the universe around us, there are fewer known processes that could give rise to positrons. "We believe we're on the threshold of discovery," said Michael Turner, a cosmologist at the University of Chicago who is not involved in the AMS project.