Web edition: March 9, 2012
Print edition: March 24, 2012; Vol.181 #6 (p. 4)
ANTI-PARTICLE DISCOVERED — Three international teams of scientists, working in the United States, Switzerland and France, have discovered and identified one of the last predicted anti-particles of matter, the anti-Xi-minus. Also known as the anti-cascade-hyperon, the tiny particle of anti-matter exists only for one ten-billionth of a second. Nevertheless, it has been observed, measured and photographed, the scientists report in Physical Review Letters, March 15, 1962. The discovery confirms the theory that there is an anti-particle for every known elementary particle.... The anti-Xi-minus is the heaviest of the predicted elementary particles to be observed. It has a positive charge.