'Antimatter factory' starts work

The Antiproton Decelerator (AD2) slows particles to a "leisurely pace"

Scientists at Europe's biggest high-energy physics laboratory have built an "antimatter factory" to study why the world is made of matter, not its mirror image.

The experiment at Cern, in Geneva, aims to produce antiatoms, and to slow them down long enough to conduct experiments on them.

It is hoped the results will explain why the world is made of matter rather than antimatter - which only occurs naturally in cosmic ray collisions.

Scientists have been puzzling for years over the disappearance of antimatter, as the Big Bang should have created the same amount of matter and antimatter, and in principle the two should have wiped each other out.

Search for a difference

The experiment will be looking closely for any difference between antimatter and matter to explain the asymmtery.

Rolf Landua: what would an antimatter Universe be like?

A spokesman for one of three antimatter projects at Cern, Rolf Landua, said: "We are looking at how the Universe would look if it was made out of antimatter. Would there be the slightest difference between our Universe and the Universe of antiatoms?"

Even a minute difference could explain why the world is made of matter, and why antimatter disappeared.

The antimatter factory cost $11.5 million to build, and consists of a circular concrete box containing a ring of high-tech magnets.

It slows antiprotons, the antimatter equivalent of the proton, down to what Cern describes as a "leisurely pace" - one tenth of the speed of light.

After trapping the antiprotons, the scientists mix them with positrons, the antimatter equivalent of the electron, to produce antihydrogen.

Precision technology

Cern succeeded in creating nine antihydrogen atoms in 1996, but they disappeared almost instantly.

"These antiprotons are an unruly bunch," said Cern spokesman Neil Calder. "They disappear the moment they touch matter.

This is the first time we'll be able to study in great precision the behaviour of antihydrogen and poke around with it because now we have the technology to hold the antihydrogen in place to study it. That's the breakthrough."

Cern hopes to have the first antihydrogen atoms by the end of 2000, and to have analysed some of the results by the end of 2002.

Two other projects on antimatter, at Stanford in California, and at a Japanese national laboratory, presented initial results last week.

Those projects do not aim to build antiatoms, but to compare the decay of antiparticles with the decay of normal particles.