York researchers part of international effort to cool a sample of antimatter to near absolute zero

The international ALPHA (Antihydrogen Laser Physics Apparatus) collaboration at CERN, which includes York University Professor Scott Menary, is touting their newest experiment made possible with a University of British Columbia built laser and research led by UBC Professor Takamasa Momose.

York University physics Professor Scott Menary, Faculty of Science

York University physics Professor Scott Menary, Faculty of Science

The researchers were able to accomplish the world’s first laser-based manipulation of antimatter, leveraging the made-in-Canada laser system to cool a sample of antimatter down to near absolute zero. The research paper was published on March 31 and is the cover story of the journal Nature. In addition to Menary, York PhD student Darij Starko is also a contributor to the research.

The novel approach taken by the international research team will significantly alter the landscape of antimatter research and advance the next generation of experiments. In a quest to discover why the Universe has so little antimatter, the researchers decided to try this unusual technique and used the laser to cool antihydrogen (the antimatter counterpart to the simplest atom, hydrogen, is a neutral antihydrogen atom, which consists of a positively charged positron orbiting a negatively charged antiproton). The original proponent of the idea was Makoto Fujiwara, ALPHA-Canada spokesperson and TRIUMF scientist.

“To cool the antihydrogen using lasers is a technical tour-de-force, which will greatly enhance our ability to measure the properties of antimatter. To achieve laser cooling is a really spectacular result,” says Menary.

The lowest energy state of hydrogen is the most accurately predicted and experimentally measured quantity in all of physics, with agreement between theory and experiment measured to the astonishing level of the 15th decimal place.

But does the same theory – Quantum Electrodynamics (QED) – apply to antihydrogen? This QED theory that so successfully describes hydrogen requires antihydrogen to have the exact same properties. That’s the goal of ALPHA, to test this aspect of the quantum description of the Universe. So far, ALPHA has measured the antihydrogen energy level to around 12 decimal places.

“We are limited to some extent by the fact that the trapped antihydrogen atoms have some residual kinetic energy. They are moving around, albeit slowly, in the trap,” says Menary. “The more we can ‘cool’ or reduce the energy of the trapped antihydrogen atoms, the more precisely we can measure it, particularly the 1S-2S transition frequency, and therefore the better we can test QED.”

The results mark a watershed moment for ALPHA’s decades-long program of antimatter research, which began with the creation and trapping of antihydrogen for a world-record one thousand seconds in 2011. The collaboration also provided a first glimpse of the antihydrogen spectrum in 2012, set guardrails confining the effect of gravity on antimatter in 2013, and showcased an antimatter counterpart to a key spectroscopic phenomenon in 2020.

The Canadian effort was led by researchers and students from ALPHA-Canada (TRIUMF, UBC, Simon Fraser University, the University of Calgary, and York University) and contributors the University of Victoria and the British Columbia Institute of Technology (BCIT).

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