Buffer-gas cooling of antiprotonic helium to 1.5 to 1.7 K, and antiproton-to-electron mass ratio
Nov 4, 20165 pages
Published in:
- Science 354 (2016) 6312, 610-614
- Published: Nov 4, 2016
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Abstract:
Charge, parity, and time reversal (CPT) symmetry implies that a particle and its antiparticle have the same mass. The antiproton-to-electron mass ratio Embedded Image 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 to . About 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, was determined as 1836.1526734(15), which agrees with a recent proton-to-electron experimental value within .- anti-p
- electron
- mass ratio
- transition: frequency
- helium: gas
- pressure: low
- cryogenics
- thermal
- beam emittance
- beam: pulsed
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