Simon Fraser University researchers involved in major international antimatter breakthrough

September 27, 2023

Antimatter is tied up in one of the world’s greatest mysteries. Physics predicts that when we create matter, we also create equal amounts of antimatter. Yet there seems to be almost no antimatter in our universe, a fact that has long puzzled physicists.

Now, physicists at Simon Fraser University, the University of Calgary, TRIUMF, the University of British Columbia, York University and the British Columbia Institute of Technology and research institutions from around the world have just answered a long-standing question that will lead to a deeper understanding of antimatter: Does it fall down? Or does it fall up?

The Antihydrogen Laser Physics Apparatus (ALPHA) collaboration at CERN, the European Organization for Nuclear Research, completed the first direct measurement of gravity’s effect on the motion of antimatter using its new ALPHA-g apparatus.

As expected by much of the scientific community, the new result confirms that antimatter does indeed fall downward. This is a tremendous scientific and technical achievement that marks a leap forward in the world of antimatter research. The collaboration’s findings are published in Nature this week.

 “Science fiction is replete with fanciful depictions of anti-gravity, including many substances and devices that block gravity, or that mysteriously fall upward. But what happens in the real world?” says SFU professor emeritus of physics Michael Hayden, a member of the ALPHA collaboration. “It isn’t surprising that it has taken so many years to get to this point. Gravity is the weakest force we know about, and at the atomic scale it is completely dwarfed by electric and magnetic interactions.”

Hayden’s expertise with magnetic fields, microwaves, and magnetic resonance experiments played a key role in confining antimatter within the instruments used for the experiment and allowing scientists to actually observe gravity’s effect on antimatter for the first time.

“Our focus at SFU has been on characterizing these magnetic fields as precisely and as quickly as possible,” he says. “We started out a decade ago focused on nuclear magnetic resonance probes, but the real workhorse for this paper turned out to be sophisticated electron cyclotron resonance experiments performed with microwaves and trapped electron plasmas.”

ALPHA has previously carried out precision measurements of the charge of antihydrogen and the frequencies of some of its most important spectral lines, which to-date match those of ordinary hydrogen. This new measurement represents the first toward performing precise measurements of the gravitational properties of antimatter, to determine if it falls in exactly the same way as matter.

What comes next? This is really just the beginning, says Hayden.

Even though it took more than a decade to plan, design, and build the apparatus and to develop the techniques to perform this experiment, Hayden and his ALPHA collaborators want to measure the gravitational interaction between matter and antimatter as precisely as possible.

“The next step will be to laser cool the antiatoms, to slow down their motions and give us more sensitivity to gravitational interactions,” he says.