Physicists make breakthrough in quest for elusive antimatter

An international team of physicists at the European Organization for Nuclear Research, or CERN, managed to create an atom of antihydrogen and then hold onto it long enough to demonstrate that it can be studied in the lab.

“For us it’s a big breakthrough because it means we can take the next step, which is to try to compare matter and antimatter,’’ said the team’s spokesman, American scientist Jeffrey Hangst.

“This field is 20 years old and has been making incremental progress toward exactly this all along the way,’’ he added. “We really think that this was the most difficult step.’’

For decades, researchers have wondered why antimatter seems to have disappeared from the universe.

Theory posits that matter and antimatter were created in equal amounts at the moment of the big bang, which spawned the universe some 13.7 billion years ago. But while matter — defined as having mass and taking up space — went on to become the building block of everything that exists, antimatter has disappeared, except in the lab.

Hangst and his colleagues, who included scientists from Britain, Brazil, Canada, Israel, and the United States, trapped 38 atoms of antihydrogen for about one-10th of a second, according to a paper submitted to the science journal Nature.

Since their first success, the team has managed to hold the antiatoms even longer.

“Unfortunately I can’t tell you how long, because we haven’t published the number yet,’’ Hangst said. “But I can tell you that it’s much, much longer than a 10th of a second. Within human comprehension on a real clock.’’

Scientists have long been able to create individual particles of antimatter such as antiprotons, antineutrons, and positrons — the opposite of electrons. Since 2002, they have also managed to lump these particles together to form antiatoms, but until recently none could be trapped for long enough to study them, because atoms made of antimatter and matter annihilate each other in a burst of energy upon contact.

Two teams had been competing for that goal at CERN, the world’s largest physics lab best known for its $10 billion smasher, the Large Hadron Collider. The collider, built deep under the Swiss-French border, wasn’t used for this experiment.

Hangst’s ALPHA team beat the rival ATRAP team led by Harvard physicist Gerald Gabrielse, who nevertheless welcomed the result.

“The atoms that were trapped were not yet trapped very long and in a very usable number, but one has to crawl before you sprint,’’ he said.

Many new techniques painstakingly developed over five years of experimental trial and error preceded the successful capture of antihydrogen.

To trap the antiatoms inside an electromagnetic field and to stop them from annihilating atoms, researchers had to create antihydrogen at temperatures less than half a degree above absolute zero.

Next, scientists plan to conduct basic experiments on the antiatom, such as shining a laser onto it and seeing how it behaves, he said.