Northwestern physicists have figured out how to trap a fast-moving, fickle particle that is notoriously difficult to study.
The scientists used electric and magnetic fields to capture, freeze and store a single positron — the antimatter counterpart of an electron. Their experiment, published early this month in the journal Physical Review Letters, allowed them to study antimatter in a controlled quantum state for months at a time.
Their discovery could make or break a longstanding theory in physics about how our universe was formed, Gerald Gabrielse the study’s lead author and the director of Northwestern’s Center for Fundamental Physics said.
“[Our work] has really captured a tremendous amount of scientific and public attention,” Gabrielse said.
Matter — the stuff we’re all made out of — contains three particles: electrons, protons and neutrons. Each of those particles also has a twin antimatter particle with the opposite electrical charge. A positron has a positive charge, while an electron has a negative charge. Whenever matter and antimatter touch, they “annihilate” each other, disappearing and turning into energy.
That’s why it’s so hard to capture antimatter, Gabrielse said. To capture it, he explained, you need a container without walls.
Gabrielse and his team created such a container with batteries and magnets to hold and freeze the positron in a resting state so that it couldn’t touch anything. They call it a “one-positron quantum cyclotron.”
“This allowed us to observe the positron, its energy levels and take really precise measurements,” Gabrielse said.
Now that Gabrielse and his team are able to observe and control a positron, they can take those measurements of its magnetic properties and compare them to a normal electron.
According to the Standard Model of particle physics, positrons should be perfect mirror images of electrons. If the positron’s measurements don’t match an electron’s, it could poke a hole in the Standard Model, which explains why our universe looks the way it does.
“The big mystery of the universe is the Big Bang should have created equal amounts of matter and antimatter,” Gabrielse said. “But, if that were true, it would annihilate, and we’d be left with nothing. There’s clearly something wrong with that theory, and that’s what we’re trying to figure out.”
And this new research could go beyond basic science.
“It would also help explain the universe and invent new technologies,” Gabrielse said. “Experiments like this are motivation to try to get a better way to describe our universe.”