A more readable article on the AMS is
http∶//www.nytimes.com/2013/04/04/science/space/new-clues-to-the-mystery-of-dark-matter.html?ref=science
The AMS measures the ratio of positrons to electrons as a function of particle energy. If the anti-matter (positrons) were the result of collisions between primordial dark-matter, the positron/electron ratio would increase with particle energy up to a certain energy level, after which the ratio would undergo a sharp decrease, (If the positrons and electrons are derived from pulsars or other later-in-time phenomena, the ratio would continue to increase with energy level.) The AMS has not yet collected enough data at high energy levels to detect the sharp drop-off to determine if the detected positrons/electrons are the residue of decay of dark matter created at the time of the big bang.
Sam Ting is an interesting character. He shared a Nobel prize for the joint (but independent) discovery of the J/psi particle. The letter "J" (Ting's choice) is a close replica of the Chinese character of his name. Not narcissistic much! The other co-discoverer, an American, selected the Greek letter "psi." Hence the particle will for ever more be known as "J/psi."
Congress mandated an additional space shuttle flight to install the AMS on the space station. It was done primarily to give NASA employees in Florida a few additional paychecks before the NASA shuttle shutdown. (The AMS experiment was not peer-reviewed.) I don't know if Congress appropriated the money for the additional flight, or whether the money came out of NASA's previously appropriated budget. It would be a shame if the latter were true.
$2B is quite a price to pay to study dark matter. Studies are being done at earth-bound laboratories and at the LHC in Geneva, but the LHC can't reach the energy levels of high-altitude cosmic collisions.
Stay tuned!