Thursday, May 6, 1999 Published at 13:34 GMT 14:34 UK
Matter or antimatter, that is the question
BaBar: Looking for the key
By BBC News Online Science Editor Dr David Whitehouse
A new experiment is designed to answer the most fundamental question about our Universe - why it is made of matter and not antimatter.
Just days later a similar Japanese experiment, Belle, will also begin. Next year an upgrade to the world's most powerful particle machine, the Tevatron at Fermilab near Chicago, will also begin work on the problem.
All the instruments will investigate the tiny differences between matter and anti-matter.
One of the great puzzles of the universe is why it is mostly made of one kind of matter instead of equal amounts of matter and anti-matter.
It is believed that the cosmos was formed with equal amounts of matter and anti-matter but today the universe is overwhelmingly made of matter. Anti-matter is rare.
Results reported earlier this year from Fermilab suggested that matter and anti-matter are not after all identical "mirror images" of one another.
This could explain why all the anti-matter that existed at the Big Bang has disappeared.
The phenomenon they think they spotted is technically called direct Charge-Parity (CP) violation. It means that particles behave differently if you swap matter for anti-matter and also swap left and right.
The observation of direct CP violation is an exciting one for physicists as it disagrees with all the currently held theories about the nature of matter. BaBar and Belle will look further into this puzzle.
The race is on
At BaBar intense beams of electrons and their anti-matter equivalent, positrons, will be smashed into each other.
After about one thousandth of a billionth of a second, these particles decay into different particles. Measuring the details of this decay process will reveal the intracacies of CP violation.
Scientists position large detectors around the point of impact of the electron-positron beam to measure this.
Looking for CP violation however will not be a swift task. It is estimated that BaBar will have to take data for at least two years before its measurement will be accurate enough.
By that time other teams, such as those at the Japanese Belle detector and the Tevatron at Fermilab near Chicago may have got the answer first.