Physicists trap a single positron in a quantum cyclotron to test the Standard Model

A Northwestern University team led by Gerald Gabrielse captured a single positron, cooled it to 300 millikelvins and held it in vacuum for months. The first one-positron quantum cyclotron lets researchers measure the particle's magnetic moment with extreme precision and compare it to the electron's.

• A positron from sodium-22 decay was cooled to 300 mK in an electromagnetic trap
• The particle was held in near-perfect vacuum for months without touching walls
• Goal is comparing positron and electron magnetic moments to one part in 10 trillion
• Any discrepancy would be the biggest physics discovery in a century