Antimatter Atoms Trapped for More Than 15 Minutes (Scientific American)

**Drew Wilson** · June 5th, 2011, 07:35 PM

Maybe antimatter is finally ready for its close-up. A team of physicists has succeeded in producing rudimentary atoms of antimatter and holding on to them for several minutes, an advance that holds hope for detailed comparisons of how ordinary atoms of matter compare with their exotic antimatter counterparts.

The researchers, from the ALPHA antimatter experiment at CERN, the European laboratory for particle physics, reported last year the first trapping of antihydrogen, the simplest antimatter atom. But the antihydrogen had at that time been confined for less than two tenths of a second. That interval has now been extended by a factor of more than 5,000. In a study published online June 5 in Nature Physics, the ALPHA group reports having confined antihydrogen for 16 minutes and 40 seconds. The more relevant number for physicists, who often deal in powers of 10, is 1,000 seconds. (Scientific American is part of Nature Publishing Group.)

The subatomic particles of everyday matter—protons, neutrons and electrons—have antimatter cousins; when matter meets antimatter the two annihilate in a burst of energy. And just as the neutral hydrogen atom is made of a single proton bound to an electron, an atom of antihydrogen comprises an antiproton and a positron, the antimatter counterparts, respectively.

But the mutual annihilation between those particles and their ubiquitous matter counterparts makes it challenging to hang on to antimatter for very long, and even more challenging to produce and confine bound atomic arrangements of multiple antiparticles. Neutral anti-atoms such as antihydrogen are especially tricky to confine because they are impervious to electric fields, which can be used to steer charged antiparticles such as antiprotons. Experiments such as ALPHA instead use superconducting magnets to trap their quarry.

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