Test of the CPT symmetry using laser spectroscopy on antiprotonic atoms

Antiprotons stopped in helium get trapped in long-living orbits making possible to study their atomic transitions via laser spectroscopy. These measurements started at CERN, Geneva, 10 years ago at the Low Energy Antiproton Ring and now continue at CERN's Antiproton Decelerator. The main result of the ASACUSA experiment is an improvement in the measurement of the antiproton mass and charge, which tests the CPT invariance when compared with those of the proton. (12 refs).