Determination of the antiproton-to-electron mass ratio by high precision laser spectroscopy of p̄He[sup +

Abstract

The ASACUSA collaboration has carried out laser spectroscopy of an antiprotonic helium atom (pHe+: 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 pHe+. By comparing the measured frequencies with three‐body QED calculations, the antiproton‐to‐electron mass ratio mp/me 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 pHe+ 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 mp/me = 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 ...