AUBURN – An international team of scientists including Auburn University physics professor Francis Robicheaux has trapped and held the antimatter version of the hydrogen atom for the first time in history. The team’s breakthrough could test fundamental physics. The journal Nature published the results of the experiment Nov. 17.
“This breakthrough is significant because it’s the first time we’ve been able to hold the atomic form of antimatter. We’re now gearing up to perform high-precision experiments on these anti-atoms,” Robicheaux said. “We’re closer to learning the very basic behavior of antimatter and why the universe is made of matter.”
The lack of antimatter in the universe remains one of the biggest mysteries of science.
The research collaboration at CERN, Europe’s particle-physics lab near Geneva, Switzerland, has confined the anti-hydrogen atoms in a magnetic trap for more than 170 milliseconds, a breakthrough in that while large quantities of the atoms were first made at CERN eight years ago, the scientists could not store them. Anti-atoms touched the ordinary-matter walls of the experiments within millionths of a second after forming and were instantly converted to energy and other particles.
“Our paper described the first positive results, so the number of particles was small, and the amount of time we held them was short. In the past month, we’ve vastly improved the trapping efficiency and the length of time the atoms are trapped,” Robicheaux said.
The progress was first made possible through the team’s ability to cool down the anti-protons to temperatures colder than the surface of Pluto, as low as minus 443 degrees Fahrenheit, or 9.26 Kelvin. In this successful experiment, the anti-proton cooler collected a large number of particles in a magnetic trap with an open top. Over time, the high-energy particles evaporated, while those with less energy remained.
When the anti-protons were mixed with the antimatter electrons, the atoms that formed were cold enough to trap. The atoms needed to be cold because the forces holding them are weak and any atom with an energy more than one degree above absolute zero would be too energetic to hold.
The ALPHA collaboration has been working toward this goal for five years. The collaboration is mainly comprised of experimentalists who designed, built and ran the experiment, including scientists from Europe, Canada, the United States, Brazil, Israel and Japan. Robicheaux serves as a theorist to the team, providing computer simulations of how mirror-trapped anti-protons might mimic anti-atom annihilations, and how actual anti-hydrogen would behave in the trap.
“One of the difficulties with the experiments is that if there were any antimatter protons left in the trap, they would look like anti-hydrogen to the detector,” Robicheaux explained. “We simulated when and where the two different types of antimatter would hit the walls and found they hit at completely different places and times. Our calculations showed we had truly trapped anti-hydrogen.”
Although Robicheaux is the only formal member of ALPHA from Auburn University, seven undergraduates have performed antimatter related research in his group.
“I’ve been lucky to have several excellent undergrads work with me,” Robicheau said.
In fact, a study done at Auburn with two undergraduates showed the method used to mix the particles would work.
“Before our calculations, the method was abandoned without being tried because it obviously wouldn’t work,” Robicheaux said. “After our calculations, they tried it out and it worked even better than we expected.”
(Contributed by Christy Kyser Truitt.)