Speaker
Prof.
Eberhard Widmann
(Stefan Meyer Institute)
Description
Recent progress in the laser and microwave spectroscopy of antiprotonic helium atoms carried out at CERN’s Antiproton Decelerator facility (AD) will be reviewed. Laser transitions were induced between Rydberg states of the exotic three-body system antiproton-electron-alpha particle. Successive refinements in the experimental techniques improved the fractional precision on the transition frequencies from 3 parts in 10^6 to <1 part
in 10^8. This progress in the experimental field was matched by similar advances in computing methods for evaluating the expected transition frequencies in three-body QED calculations. The comparison of experimental and theoretical frequencies for seven transitions in antiprotonic heium-4 and five in antiprotonic heium-3 yielded an antiproton-to-electron mass ratio of 1836.152 674(5). This agrees with the known proton-to-electron mass ratio at the level of ~3× 10^−9. The experiment also sets a limit on any CPT-violating difference between the antiproton and proton charges and masses of the same value.
The hyperfine structure of a state in antiprotonic helium has also been measured by microwave spectroscopy with increasing precision, from 3x10^-5 in 2001 to 2x^10^-6 in 2008 for the two allowed M1 transitions. This is one order of magnitude more accurate than the most precise three-body QED calculation. The difference of the two observed tranistion frequencies, which is directly sensitive to the antiproton magnetic moment, has been determined to about the theoretical accuracy (relative precision 1x10^-3). A more detailed analysis together with increases in the theoretical precision may soon yield an improvement in the value of the antiproton magnetic moment.
Author
Prof.
Eberhard Widmann
(Stefan Meyer Institute)
Co-authors
Prof.
Dezso Horvath
(KFKI Research Institute for Particle and Nuclear Physics)
Dr
Masaki Hori
(Max Planck Institute for Quantum Optics)
Prof.
Ryugo S. Hayano
(University of Tokyo)
Mr
Thomas Pask
(Stefan Meyer Institute)