Determination of the antiproton-to-electron mass ratio by high precision laser spectroscopy of anti-He+

Aug 18, 2008

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20202021202201
Abstract: (AIP)
The ASACUSA collaboration has carried out laser spectroscopy of an antiprotonic helium atom ( p ̄ He + : a Coulomb three‐body system consisted of an antiproton, electron, and a helium nucleus) at CERN's Antiproton Decelerator facility and measured transition frequencies of p ̄ He + . By comparing the measured frequencies with three‐body QED calculations, the antiproton‐to‐electron mass ratio m p ̄ /m e was determined. We recently developed a new laser system consisting of single‐mode continuous‐wave lasers, a femtosecond optical frequency comb, a pulse‐amplified dye laser, and a chirp compensation, and achieved a precision of ∼1×10 −8 on the p ̄ He + transition frequencies, which was about one order of magnitude improvement. The comparison of the measured frequencies and the three‐body QED calculations yielded the antiproton‐to‐electron mass ratio of m p ̄ /m e  = 1836.152 674(5). Combined with a constraint on the proton and antiproton charge‐to‐mass ratio of the TRAP group, a limit on any CPT ‐violating difference between the antiproton and proton charges and masses was also set as |Q p +Q p ̄ |/Q p ∼|m p −m p ̄ |/m p <2×10 −9 at a confidence level of 90%.
  • 12.20.-m
  • 25.43.+t
  • 42.62.Fi
  • hadronic atoms
  • spectroscopy
  • quantum electrodynamics
  • p: charge
  • laser
  • mass ratio: (electron anti-p)
  • quantum electrodynamics
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