AMS hints at cosmic-ray mystery
Jun 11, 1999
The first particle-physics experiment to fly in space, the Alpha Magnetic Spectrometer (AMS), has detected four times as many positrons as electrons at an energy of 1 GeV around the Earth's equator, instead of finding equal numbers as predicted. The results were announced by project leader Sam Ting at the recent Inner Space/Outer Space symposium at Fermilab in the US. The AMS gathered about 100 hours of data onboard the US Space shuttle last June and will be permanently installed on the International Space Station in 2003.
The experiment also found that changes in the strength of the Earth's magnetic field with latitude do not alter the number of low-energy protons hitting the Earth's atmosphere. However the experiment failed to detect any anti-helium atoms among the three million ordinary helium atoms that it detected. The two main goals of the experiment are to detect anti-matter left over form the big bang (as opposed to anti-matter created by high-energy cosmic rays crashing into particles in space), and to detect "dark matter" particles. As much as 99% of the universe is thought to be made up of dark matter but it is difficult to detect because it does not emit radiation (hence the name dark).
The AMS project is a collaboration between 37 research institutions in China, Finland, France, Germany, Italy, Portugal, Romania, Russia, Spain, Switzerland, Taiwan, Korea and the United States.