Spectroscopy of the hyperfine structure of antiprotonic ~4He and ~3He

摘要

The spin magnetic moment μ_s~p of the antiproton can be determined by comparing the measured transition frequencies in p~4He~+ with three-body QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as μ_s~p = -2.7862(83)μN, slightly better than the previously best measurement. This agrees with μ_s~p within 0.24%. In 2009, a new measurement with antiprotonic 3He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on p~3He~+. We report here on the new experimental setup and the first tests.