Researchers 'look inside' antimatter

In its so-called Atrap research, the Cern team has built a corral for anti-protons

European scientists have carried out the first experiments on antimatter.

Researchers in Geneva, Switzerland, have been able to trap and control anti-hydrogen atoms in a chamber at a sufficiently low temperature to begin studying their physics in detail.

They say the development should help them get a better understanding of how antimatter differs from normal matter and why the latter has come to dominate the Universe around us.

According to mainstream thinking, equal amounts of matter and anti-matter should have been created in the Big Bang at the beginning of time - and then annihilated each other in a flash of energy.

Quite why one form won out over the other has yet to be explained.

Large quantities

Anti-matter is like a mirror image of normal matter in that their constituent parts have apparently opposite properties.

This work is important because it will enable us to understand why there is any matter at all in the Universe

Mike Charlton

In the simplest normal element, hydrogen, a negatively charged electron orbits a proton nucleus; but in an anti-hydrogen atom, a positively charged particle - a positron - orbits an anti-proton nucleus.

Researchers at the European Nuclear Physics Research Centre (Cern) recently announced they had the ability to make anti-atoms of hydrogen in substantial quantities.

Now they say they can store these fragile objects for study as well, allowing them to conduct simple experiments.

Mike Charlton, who works at Cern, told the BBC: "This work is important because it will enable us to understand why there is any matter at all in the Universe. This is one of the great mysteries.

"This work gives us a whole new avenue to explore that didn't exist a few weeks ago."

'fundamental test'

The Cern researchers created the antimatter by accelerating particles to near the speed of light and then crashing them on to a plate.

One in a million of the resulting fragments is suitable for making anti-atoms. Anti-protons are collected and stored in a cloud of low-energy positrons, which act like a fridge, cooling the particles down until they combine into anti-atoms.

Research team member Walter Oelert said: "In 1996 we produced only a few atoms of anti-hydrogen at a velocity close to the speed of light, which is equivalent to a temperature 100,000 times that of the inner part of the Sun.

"You can imagine that this material is too hot to handle. Now, we have anti-hydrogen in much larger quantities as cold as only a few degrees above absolute zero."

In their first experiments on anti-hydrogen, the research team broke up their newly created atoms using an electric field.

By measuring the strength of the electric field, they hope to tell how tightly an anti-atom is held together and shed light on the differences between normal matter and antimatter that might explain why the Universe exists in its present form.

Cern physicist Jerry Gabrielse said: "Our long-term goal is to try to look very precisely at this anti-atom, and by comparing the world's simplest antimatter atom and the world's simplest matter atom to make a very fundamental test of basic physics theories."

The research is being published in the journal Physical Review Letters.