# ALPHA measures charge of antihydrogen

23 July 2014

The ALPHA experiment at CERN’s Antiproton Decelerator (AD) has made a new precision measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places. This is the first time that the charge of an antiatom has been measured to high precision. The ALPHA collaboration studied the trajectories of antihydrogen atoms released from the experiment’s system of particle traps in the presence of an electric field. If the antihydrogen atoms had a charge, the field would deflect them. The analysis, based on 386 events, gives the value of the antihydrogen electric charge as (–1.3±1.1±0.4) × 10–8.