Antimatter atoms trapped for 16 minutes

Antimatter atoms have been held captive and kept in existence for a whopping 16 minutes by a Canadian-led team far longer than the researchers thought possible.

"It was quite a surprise," said Makoto Fujiwara, lead author of a study published Sunday in Nature Physics.It reported trapping antiatoms of antihydrogen the antimatter counterpart of a hydrogen atom for 1,000 seconds.

Antimatter is made up of "antiparticles" that have the same mass as corresponding particles of matter, but an opposite charge. For example, the antimatter counterpart of a negatively charged electron is a positively charged positron.

Antimatter is very difficult to keep in existencebecause the moment it touches matter, which makes up most of our universe, both the matter and antimatter are annihilated, producing pure energy.

The scientists' recent achievement has extended the experimental lifetime of antihydrogen atoms 5,000-fold since the ALPHA experiment an international collaborationFujiwara is part of first figured out how to trap them at all.

The team, based at the laboratory of CERN, the European organization for nuclear research, near Geneva,published its method in Nature last November. At the time, it reported that it had held onto the antiatoms for less thanone-fifth of a second.

Holding antiatoms captive for several minutes opens up a new range of possible experiments to probe the nature of antimatter,said Fujiwara, a research scientist at Vancouver-based TRIUMF and an adjunct professor at the University of Calgary.

'Game changer'

Scientists will more easilybe able to do experiments to compareantihydrogento hydrogen andcould even potentially test howantimatter atoms areaffected bygravity, he added. "I call it a game changer."

Antihydrogen is made by mixing antiparticles called antiprotons (the antimatter counterparts of protons)and positrons (the antimatter counterparts of electrons). In recent months, Fujiwara said, theALPHA team has figured out how tocreate very cold antiparticlesand mix them more gently to produce and trap antiatoms more efficiently, successfully trapping an average of one antiatom per trial.

They also decided to test how long they could keep the antiatoms trapped. Fujiwara thought holding on to them for several seconds might be possible and was stunned that they could survive for many minutes.

That will make it much easier to do experiments to compare antihydrogen to hydrogen, he added.

For example, researchers can point lasers and microwaves at the antiatoms and figure out how the colours of light they shine back compare to those shone back by hydrogen atoms under the same circumstances, Fujiwara said.

Aiming the lasers and microwaves precisely at the antiatoms using the right settings is very difficult right after the antiatoms are formed because they are in what's called an excited state the positrons are orbiting the nucleus of the antiatom, but they're very far away, and they're constantly changing their orbit.

Over time, they reach a stable orbit close to the nucleusknown as the "ground state." That allows the lasers and microwaves to be aimed with high precision. Theoretical calculations show that after several minutes, the antiatoms should all be in the ground state.

Studying the effect of gravity on antimatter is particularly challenging because gravity acts so weakly compared to other forces on particles with such a tiny mass, so a lot of time is needed.

"The possibility of studying gravitational effects really become feasible now," Fujiwara said. "Thats something Im personally interested in pursuing."

About one-third of the40 physicists who make up the ALPHA collaboration are Canadian. The rest are fromBrazil, Denmark, Israel, Japan, Sweden, the U.K. and the U.S.

Canadian funding for the projectcomes from NSERC (Natural Sciences and Engineering Research Council, TRIUMF, AIF (Alberta Ingenuity Fund), the Killam Trust, and FQRNT (Le Fonds qubcois de la recherche sur la nature et les technologies).