WEDNESDAY, 4 MAY 2011.
A number of different antimatter species are produced by heavy-ion collisions; the most common are the least massive because it takes the least energy to create them. As a result, the antielectron was the first antiparticle to be detected, in cosmic ray debris in the 1950s, followed by antiprotons and antineutrons. Only now have antihelium particles, having baryon number 4 (two antiprotons and two antineutrons), been found.
The next stable antimatter nucleus would be antilithium, whose production rate in a particle accelerator is expected to be over two million times less than antihelium. A breakthrough in accelerator technology will be needed to detect it .
Written by Robert Jones