Particle physics: Homing in on the properties of antimatter

High-precision measurements of a physical property of antihydrogen that has previously only been predicted by theory are reported in Nature this week. The observations, made by the ALPHA collaboration at CERN, are consistent with theory and correspond with the properties of hydrogen. This finding highlights symmetries between matter and antimatter.

Probing and comparing the properties of matter and antimatter could help us to understand the formation of the Universe, where matter is more common than antimatter. The fine structure of hydrogen (the simplest atom) has been well studied, but not for its counterpart, antihydrogen.

Jeffrey Hangst and colleagues report the observation of the Lamb shift - an effect originally observed in hydrogen that demonstrates a difference in energy levels within the fine structure of the hydrogen spectrum - in antihydrogen. Their measurements match what has been seen in hydrogen and predictions made about antihydrogen, providing a test of a fundamental symmetry of nature. In an accompanying News & Views article, Randolf Pohl notes that these measurements could open the door for further investigations of antihydrogen. For example, it may be possible to examine the quantum electrodynamical properties of antihydrogen or perform targeted tests of the standard model of particle physics.