Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007rpph...70.1995h&link_type=abstract
Reports on Progress in Physics, Volume 70, Issue 12, pp. 1995-2065 (2007).
Physics
23
Scientific paper
We review recent progress in the laser and microwave spectroscopy of antiprotonic helium atoms (\barpHe^+ \equiv \rme^\--\barp - He^{++}) carried out at CERN's Antiproton Decelerator facility (AD). Laser transitions were here induced between Rydberg states (n, ell) and (n ± 1, ell - 1) of \barpHe^+ (n ~ 40 and ell ≲ n - 1 being the principal and orbital angular momentum quantum numbers of the antiproton orbit). Successive refinements in the experimental techniques improved the fractional precision on the \barpHe^+ frequencies from 3 parts in 106 to ~1 part in 108. These included a radiofrequency quadrupole decelerator, which reduced the energy of the antiprotons from 5.3 MeV (the energy of the beam emerging from AD) to ~100 keV. This enabled the production of \barpHe^+ in ultra-low density targets, where collisional effects with other helium atoms are negligible. A continuous wave pulse-amplified dye laser, stabilized against a femtosecond optical frequency comb, was then used to measure the \barpHe^+ frequencies with ppb-scale precision. 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 (νexp) and theoretical (νth) frequencies for seven transitions in \barp^4He^+ and five in \barp^3 He^+ yielded an antiproton-to-electron mass ratio of m_\bar p/m_{\rme} = 1836.152\,674(5) . This agrees with the known proton-to-electron mass ratio at the level of ~2 × 10-9. The experiment also set a limit on any CPT-violating difference between the antiproton and proton charges and masses, (Q_p - |Q_{\barp}|)/Q_p \sim (m_p - m_{\barp})/m_p < 2 \times 10^{-9} to a 90% confidence level. If on the other hand we assume the validity of the CPT invariance, the m_{\barp}/m_{\rme} result can be taken to be equal to mp/me. This can be used as an input to future adjustments of fundamental constants. The hyperfine structure of a state in \barp^4He^+ has also been measured by microwave spectroscopy to a precision of 3 × 10-5. This corresponds to the accuracy of the most precise three-body QED calculations. Further increases in the experimental precision may soon yield an improvement in the value of the antiproton magnetic moment.
Hayano Ryugo S.
Hori Masaki
Horváth Dezso
Widmann Eberhard
No associations
LandOfFree
Antiprotonic helium and CPT invariance does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Antiprotonic helium and CPT invariance, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antiprotonic helium and CPT invariance will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1027371