By Peter Weiss
As theorists see it, the universe exploded into being billions of years ago with equal parts matter and antimatter. Yet aside from traces produced in laboratories and detected in the atmosphere and space, nearly no antimatter exists now. Physicists at particle accelerators in California and Japan have now taken a step closer to understanding that puzzling absence.
New data from those accelerators, combined with older American results, raise to two the number of elementary particle types in which matter and antimatter have been observed to break down in different ways, scientists say.