Münster 2002 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HK: Physik der Hadronen und Kerne
HK 24: Nuclear Physics / Spectroscopy III
HK 24.3: Vortrag
Mittwoch, 13. März 2002, 11:45–12:00, B
Observation of microwave-induced transitions between hyperfine levels of antiprotonic helium — •Eberhard Widmann — Department of Physics, University of Tokyo
The ASACUSA collaboration at the Antiproton Decelerator of CERN succeeded in the year 2001 for the first time to observe two microwave-induced transitions between hyperfine levels of antiprotonic helium. The hyperfine levels are those of a highly excited state (principal quantum nunber 37, angular quantum number 35) of the exotic three-body system p–e−–He2+. The observed transitions at ∼ 12.91 GHz correspond to an electron spin flip in the orbital magnetic field of the antiproton. The experimental accuracy is ∼ 1.5 × 10−5, and the measured frequencies agree with three-body QED calculations on the level a few 10−5. The current precision of the theory is limited by the omission of terms of order α2 ≈ 5 × 10−5 which is worse than the experimental resolution.
This constitutes the first precise measnurement of the orbital magnetic moment of a composite particle. In addition to providing a benchmark for three-body QED calculations, the hyperfine structure of antiprotonic helium is sensitive to the magnetic moment of the antiproton, an important quantity related to CPT invariance. An increased accuracy of both experiment and theory may yield an improved value of the antiproton magnetic moment which is only known with an accuracy of 3 × 10−3.