Physicists Trap Antimatter Particle for Extended Studies
Researchers at Northwestern University have isolated a positron for months, opening new avenues in particle physics research.
Physicists at Northwestern University have made a breakthrough by successfully trapping a single positron, the antimatter counterpart of the electron, for months. This achievement allows them to conduct detailed quantum measurements on the particle.
The study, reported in Physical Review Letters, is crucial in understanding why our universe is composed predominantly of matter instead of antimatter. Gerald Gabrielse, a physicist at Northwestern and senior author of the study, remarked, “The big challenge is to persuade these positrons to slow down and then capture them.” This is essential as antimatter particles typically annihilate upon contact with matter.
To trap the positron, researchers utilized a radioactive isotope of sodium-22, which decays and emits positrons. The process began by directing the positrons through a slab of cold tungsten. As they passed through the crystal lattice, they slowed down significantly, reducing the chance of annihilation. Those that survived emerged less energized, allowing them to be funneled into a vacuum trap.
The trap operates just above absolute zero, using a combination of electric and magnetic fields to keep the positron contained without physical walls. Gabrielse explained, “If you want to hold on to antimatter, you have to hold it in a container without walls.” This method enabled the researchers to maintain the positron for an extended period, facilitating unprecedented studies.
Future investigations aim to measure the positron’s magnetic moment, which involves determining how much energy is required to flip its spin direction and transition it to higher energy states. Such measurements will allow comparisons with the electron’s magnetic moment, which Gabrielse’s team previously measured to an astounding precision of one part in 10 trillion. They hope to find if the positron exhibits an opposite magnetic moment to the electron, as predicted by the Standard Model of particle physics.
Roni Harnik, a theoretical physicist at the Fermi National Accelerator Laboratory, noted, “This is an exciting development that will enable us to test a basic symmetry.” If discrepancies arise in the magnetic moments of matter and antimatter, it may provide insights into why our universe has a surplus of matter.
This endeavor is part of a broader scientific effort to explore the fundamental reasons behind the imbalance between matter and antimatter, a question that has baffled physicists since the Big Bang.
