Revealing Our Antimatter Universe--1st Measurement Ever of an Antimatter Atom

We may soon know why the universe seems to have a preference for matter over antimatter.An international team of physicists working on the ALPHA experiment at CERN near Geneva, Switzerland, has successfully used microwaves to manipulate antihydrogen atoms. Their work could help answer fundamental questions about the universe. The accomplishment, by physicists working on the ALPHA experiment at CERN near Geneva, Switzerland, is a first step towards more detailed measurements that will reveal whether matter and antimatter are true mirror images.

"This comparison is motivated in part by a question that has baffled scientists for a long time," says Simon Fraser University physics professor Mike Hayden, lead author of the research paper published in Nature March 7. "The known laws of physics tell us that matter and antimatter should naturally exist in equal amounts. The problem is that we seem to live in a universe that is almost entirely devoid of antimatter. A possible explanation is that there might be some subtle difference between matter and antimatter, which let matter win out over time as the universe evolved. If a difference between hydrogen and anti-hydrogen is discovered, it could provide a valuable clue for solving this mystery."

The ALPHA team trapped an atom of antihydrogen --made up of a positron - the antimatter equivalent of an electron and an antiproton-- using magnetic fields. By shining microwave radiation tuned to a specific frequency on the captive atom, the team was able to flip the anti-atom's magnetic moment, liberating it from the trap and allowing it to be detected, enabling the first spectroscopic measurement of antihydrogen.

The current standard model of particle physics predicts that antimatter atoms should behave exactly the same as atoms of normal matter, and have identical properties, apart from their opposite charge, which can be verified by comparing the frequency of light emitted from excited atoms. Any difference in these spectroscopic measurements would suggest that antimatter is not an exact opposite of matter - and the assumptions the standard model is based on would be considerably weakened.

The present measurement, which was conducted by the ALPHA collaboration at CERN in Switzerland, involved irradiating magnetically-trapped anti-atoms with microwaves. Precise tuning of the microwave frequency and magnetic field enabled researchers to hit an internal resonance, kicking atoms out of the trap and revealing information about their properties.

"We have just witnessed the first-ever interactions between microwaves and trapped antimatter atoms," says Hayden. The Daily Galaxy via Simon Fraser University. Eventually measurements may reveal clues that may help solve one of the deepest mysteries in particle physics.

The Daily Galaxy via Simon Fraser University and newscientist.com

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