Physicists have tightened the limits on the possible charge of an atom of antihydrogen.

The neutral charge on many atoms and molecules has been measured with extremely high precision. The standard model of physics says that hydrogen's antimatter counterpart should have an opposite charge and so be neutral to a similar level. Any differences between the two could help to explain why the Universe contains more matter than antimatter.

Joel Fajans at the University of California, Berkeley, and his colleagues used data from previous experiments to analyse the influence of electric fields on antihydrogen atoms released from a magnetic trap. They found that the atom was charge-neutral, with a limit 1 million times lower than the best previous figure.

Nature Commun. http://dx.doi.org/10.1038/ncomms4955 (2014)