COLLOQUIUM: Antihydrogen - a tool to study matter-antimatter symmetry in the laboratory (Sep 2016)

Speaker: Eberhard Widmann, Austrian Academy of Sciences

Abstract:
Antihydrogen, the bound state of an antiproton and a positron, is the simplest atom consisting purely of antimatter. Its matter counterpart, hydrogen, is one of the best studied atomic systems in physics. Thus comparing the spectra of hydrogen and antihydrogen offers some of the most sensitive tests of matter-antimatter symmetry. Furthermore, the availability of neutral antimatter offers for the first time a precise measurement of its gravitational interaction that was so far not possible due to the dominance of the electro-magnetic interaction for charged antiparticles.

The formation and experimental investigation of antihydrogen is the main physics goal of several collaborations at the Antiproton Decelerator of CERN. The ASACUSA collaboration is pursuing a measurement of the ground-state hyperfine structure of antihydrogen in an atomic beam, a quantity which was measured in hydrogen using a maser to a relative precision of 10^{-12}. The AEgIS collaboration aims at using an ultra-cold beam of antihydrogen atoms and a classical moiré deflectometer to determine the gravitational interaction between matter and antimatter in a first step to several percent precision.

After a first production of cold antihydrogen in 2002 and a first trapping in 2010 the experiments are still in the process of optimising the antihydrogen production from trapped antiprotons and positrons. The status and prospect of these experiments will be reviewed.