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SYAM: Symposium Atomic Anti-Matter Physics

SYAM 1: Atomic Anti-Matter Physics I

SYAM 1.1: Invited Talk

Thursday, March 9, 2017, 11:00–11:30, P 1

Buffer gas cooling of antiprotonic helium to T=1.5-1.7 K, and the antiproton to electron mass ratio — •Masaki Hori — Max-Planck Institute for Quantum Optics, Garching, Germany

The antiproton-to-electron mass ratio can be precisely determined from the single-photon transition frequencies of antiprotonic helium. We measured 13 such frequencies with laser spectroscopy to a fractional precision of 2.5 to 16 ppb. About two billion antiprotonic helium atoms were cooled to temperatures between 1.5 and 1.7 kelvin by using buffer-gas cooling in cryogenic low-pressure helium gas; the narrow thermal distribution led to the observation of sharp spectral lines of small thermal Doppler width. The deviation between the experimental frequencies and the results of three-body quantum electrodynamics calculations was reduced by a factor of 1.4 to 10 compared with previous single-photon experiments. From this, Embedded Image was determined as 1836.1526734(15), which agrees with a recent proton-to-electron experimental value within 0.8 ppb.