Physicists Trap Single Antimatter Particle for Months

Physicists have successfully trapped a single subatomic antimatter particle for months at a time, achieving a breakthrough that could help researchers study its quantum states and investigate why the universe is predominantly made of matter. When antimatter and matter meet, they typically annihilate each other, making the substance notoriously difficult to examine in a standard laboratory environment.

Every ordinary particle of matter possesses an antimatter counterpart carrying equal mass but opposite charge. To construct their specialized container, the research team began with sodium 22, a radioactive isotope possessing a half-life of approximately two and a half years. As these atoms decay, they emit positrons, which serve as the antimatter counterparts to electrons.

The primary obstacle involved convincing the positrons to decelerate before capturing them. Gerald Gabrielse, a physicist at Northwestern University who oversaw the project, noted that the big challenge was persuading these particles to slow down. The team published their findings in Physical Review Letters.

To achieve this, the physicists directed the positrons through the crystal lattice of a thin tungsten slice cooled to low temperatures. While pinballing through the material, the particles lost energy, and although many annihilated upon impact, some successfully emerged at the far end. Electromagnetic fields then guided the surviving positrons into a vacuum maintained just three tenths of a degree Celsius above absolute zero.

Inside this vacuum, an electric field positioned on the top and bottom alongside a magnetic field on the sides successfully confined the particles without physical walls. This isolation allowed the team to hold a solitary positron for a month, opening the possibility of indefinite containment. The researchers intend to use the setup to measure the positron's magnetic moment precisely, determining the energy required to flip its spin and shift it to an excited state.

By comparing the positron's magnetic moment with that of an electron, which Gabrielse and his colleagues previously measured to a high degree of precision, the team aims to test predictions of the Standard Model of particle physics. Discrepancies between the two values could shed light on why matter survived the massive annihilations that followed the Big Bang, leaving behind the stars and planets visible today.

Roni Harnik, a theoretical physicist at the Fermi National Accelerator Laboratory who was not involved in the project, described the achievement as an exciting development that allows scientists to test basic symmetries. If measurements reveal differences between matter and antimatter, it could finally resolve one of the most profound mysteries in cosmology.