Physicists at Northwestern University have trapped a single particle of antimatter and kept it suspended in a magnetic cage for months, cooling it to the lowest energy state physics allows.
The particle is a positron, the antimatter counterpart of the electron. The team, led by physicist Gerald Gabrielse, held it in an electromagnetic trap cooled to about 300 millikelvins, barely above absolute zero, where the positron never touches anything. The work was detailed in Physical Review Letters on October 21.
Catching the positron was the hard part, Gabrielse said. The positrons emerged at enormous energies from the decay of sodium-22, a rare radioactive isotope of sodium, and the team slowed them through a tungsten crystal before guiding a single one into the trap’s near-perfect vacuum. “We actually coaxed this very fast positron to sit there and behave for months at a time,” he said.
The goal is to measure the positron’s magnetic properties with unprecedented precision and compare them against its matter counterpart. The Standard Model predicts the Big Bang should have created equal amounts of matter and antimatter, yet the universe is made overwhelmingly of matter. Finding a mismatch, Gabrielse said, “would be revolutionary in physics.” Antimatter physicist Barbara Maria Latacz of CERN called the experiment “a remarkable achievement” that will be “a powerful probe for physics beyond the Standard Model,” while Stefan Ulmer of Heinrich Heine University Dusseldorf said he could not wait to see the first precision measurements.
Source: Nature
