Northwestern traps a positron for months, opening a precise test of matter–antimatter symmetry
Physicists at Northwestern University trapped a single positron—the antimatter counterpart of an electron—for months, cooled it to 300 millikelvins and controlled and detected its quantum energy states. The team, led by Gerald Gabrielse, plans to measure the positron’s magnetic moment and compare it with the electron’s; a difference would challenge predictions of the Standard Model, according to Phys.org.
Bottom line — The positron’s magnetic moment measurement is still ahead; the team hopes to report a result early next year, ScienceAlert reports.
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The team produced positrons using radioactive sodium-22, then slowed them in a tungsten crystal before guiding them into a Penning trap, ScienceAlert reports.
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Electric and magnetic fields hold the particle in a vacuum without contact with matter, which would annihilate it, according to Phys.org.
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Carefully tuned microwaves let the researchers move the positron between quantum energy levels and detect those transitions, Phys.org reports.
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The team previously measured the electron’s magnetic moment to about one part in 10 trillion, according to Scientific American.
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The researchers’ target is to compare the electron and positron magnetic moments, which the Standard Model predicts should have equal magnitudes and opposite signs, ScienceAlert reports.