Precision laser spectroscopy experiments on antiprotonic helium
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany
* e-mail: Masaki.Hori@mpq.mpg.de
Published online: 25 June 2018
At CERN‘s Antiproton Decelerator (AD) facility, the Atomic Spectroscopyand Collisions Using Slow Antiprotons (ASACUSA) collaboration is carrying out precise laser spectroscopy experiments on antiprotonic helium (p̅He+ ≡ p̅+He2++e−) atoms. By employing buffer-gas cooling techniquesin a cryogenic gas target, samples of atoms were cooled to temperatureT = 1.5–1.7 K, thereby reducing the Doppler width in the single-photon resonance lines. By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was determined as Mp̅/me = 1836.1526734(15). This agreed with the known proton-to-electron mass ratio with a precision of 8 . 1010. Further improvements in the experimental precision are currently being attempted. The high-quality antiproton beam provided by the future Extra Low Energy Antiproton Ring (ELENA) facility should further increase the experimental precision.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.