ANTIMATTER, the most elusive building block of the Universe, has 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. Seven antihydrogen atoms were detected in a particle
accelerator at Fermilab near Chicago in 1996, but they were moving at almost the
speed of light—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. 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.
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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.