Antimatter atoms, among the most elusive matter in the Universe, have been captured for the first time.
According to the standard model of particle physics, every particle has a corresponding antiparticle with the same
mass and opposite charge. The pair annihilate each other on contact, releasing a burst of energy.
Scientists have wondered if they can harness this energy, but they have found it difficult to make and control antiatoms.
In the late 1990s, up to nine antihydrogen atoms were detected in particle accelerators at CERN and at Fermilab near Chicago.
But they were moving at almost the speed of light - much too fast to be stored or studied.
Now researchers on the ATRAP experiment at CERN, the European Laboratory for Particle Physics near Geneva, think they
have made and stored thousands of antiatoms indefinitely in a particle trap.
Cup of coffee
The team, led by Gerald Gabrielse of Harvard University, used powerful magnetic fields to trap antiprotons found
in the debris of collisions in CERN's particle accelerator. They then introduced a beam of antielectrons, or positrons,
and used an electric field to slow them down and bring the two types of particle together.
When the group exposed the particle trap to an electric field, some particles failed to move, suggesting that the charged
antiparticles had bound together into neutral antihydrogen atoms.
"It's hard to see how you could avoid having some antihydrogen in there," says Gabrielse. He can't be sure how many atoms they
trapped, but says you would get only a tiny amount of energy by combining the antimatter with matter--not even enough to
warm a small cup of coffee.
Gabrielse hopes to confirm the find by measuring the antihydrogen atom's spectrum when CERN's particle accelerator
starts running again next May.
The new research was presented at the American Association for the Advancement of Science's 2002 annual meeting in Boston.