Global Competition Between Scientists Trying to Decode...

The Mystery of Antimatter


Antimatter Atoms Experiments Planned
By Naomi Koppel

Source: Associated Press

August 10, 2000

GENEVA (AP) - European scientists searching for answers to some of science's most basic questions announced plans Thursday to build atoms of antimatter and then ``cage'' them for use in experiments.

The researchers at the European Laboratory for Particle Physics, or CERN, said they plan to make atoms of antihydrogen. It would be the first time that antiatoms have been slowed down enough to be caught and studied, intensifying global competition between scientists trying to decode the mystery of antimatter.

Physicists believe that antimatter is the mirror image of conventional matter in the universe. For every subatomic particle in the universe, there appears to be another identical in appearance and structure, but with its electric or magnetic properties reversed.

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

But somehow there was enough matter left over to create the universe, and antimatter only exists now in cosmic rays and particle accelerators.

CERN, famed for its 16 3/4-mile particle accelerator, this time is using a small decelerator - 616 feet around - to create its ``antimatter factory.''

The CERN scientists plan to test the antihydrogen atoms to see if they behave in the same way as ordinary hydrogen.

``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?'' said Rolf Landua, spokesman for one of three projects at CERN looking at the issue.

If antimatter differs from matter, even by one part in a hundred billion, that could explain why the world is made up of matter and why antimatter has disappeared, he added.

The decelerator takes antiprotons - the opposite of protons- which have been created in the accelerator, groups them together and then slows them down to a tenth the speed of light.

These can then be captured, either in electromagnetic fields or by inserting them into ordinary atoms, which is possible because antiprotons destroy normal protons but not other matter.

Then, positrons - antielectrons emitted by a radioactive source - are added to the antiprotons. Just as one proton and one electron creates hydrogen, so one antiproton and one positron creates antihydrogen.

The antihydrogen is then stored at very low temperatures and laser beams are shot at it to see if it behaves differently from hydrogen. Scientists want to know if antiatoms have a slightly different attraction to each other compared with ordinary atoms.

``We hope to have the first antihydrogen atoms by the end of this year, and we will then have to construct a new type of apparatus in order to trap them. We aim to give a first analysis by the end of 2002,'' Landua said of the project, called ATHENA.

``It could give us a clue to why our universe exists, but it isn't clear what that clue might be. We ask a question, nature gives us an answer, and if we're clever enough we understand the answer.''

The CERN project is one of three major international efforts trying to solve the mystery of the disappearance of antimatter. Two projects - BaBar at the Stanford Linear Accelerator Center in California and Belle, based at KEK, a Japanese national laboratory - presented their initial results last week.

Those projects do not aim to build antiatoms, but instead to measure how antiparticles decay to see how this compares with the decay of normal particles.

Physicists in the United States said the CERN effort to manufacture antiatoms is the next step to understanding the fundamental properties of an antimatter world.

``To really understand whether this mirror world is out there, you have to test its ingredients and see if they behave the way we would expect them to behave,'' said Kurt Riesselmann, a physicist and spokesman for the Fermi National Accelerator Laboratory outside Chicago.

When they collide, matter and antimatter release tremendous energy. Some scientists dream of harnessing this energy to send spacecraft to other solar systems orbiting distant stars.

However, Riesselmann said antimatter propulsion and other practical applications of the mirror world is a long way off. The CERN experiments would trap small amounts of antimatter in magnetic fields for experiments, but that wouldn't be practical on a larger scale.

``How would you store it?'' he said. ``You couldn't put it in a vessel or a container made of matter.''


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