Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio

@article{Hori2011TwophotonLS,
  title={Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio},
  author={Masaki Hori and Anna O. Soter and D{\'a}niel Barna and Andreas J Dax and Ryugo Hayano and Susanne Friedreich and Bertalan Juh{\'a}sz and Thomas Pask and Eberhard Widmann and Dezso Horvath and Luca Venturelli and Nicola Zurlo},
  journal={Nature},
  year={2011},
  volume={475},
  pages={484-488}
}
Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (He+) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton () occupying a Rydberg state with high principal and angular momentum quantum numbers… 
Two-photon spectroscopy of antiprotonic helium
The precision of laser spectroscopy of antiprotonic helium (a helium atom with one of its electrons replaced by an antiproton) has improved by almost 4 orders of magnitude over its 20 years of
Two-photon laser spectroscopy of antiprotonic helium atoms, and the antiproton-to-electron mass ratio
Some two-photon transitions in antiprotonic helium atoms at the deep UV wavelengths ? = 139.8?197.0 nm were recently studied by laser spectroscopy. The thermal Doppler broadening of the observed
Sub-Doppler Two-Photon Laser Spectroscopy of Antiprotonic Helium and the Antiproton-to-Electron Mass Ratio
The ASACUSA collaboration of CERN has recently irradiated antiprotonic helium atoms with two counter-propagating laser beams. This excited some non-linear two-photon transitions of the antiproton at
Recent progress of laser spectroscopy experiments on antiprotonic helium
  • M. Hori
  • Physics
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
  • 2018
TLDR
By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was determined as , which agrees with the known proton- to-electrons mass ratio with a precision of 8×10−10.
Buffer-gas cooling of antiprotonic helium to 1.5 to 1.7 K, and antiproton-to–electron mass ratio
TLDR
The extracted mass of the antiproton (relative to the electron mass) was in good agreement with previous measurements of the proton mass, in keeping with the implications of the combined charge, parity, and time-reversal symmetry of physical laws.
Determination of the Antiproton-to-Electron Mass Ratio by Two-Photon Laser Spectroscopy of Antiprotonic Helium Atoms
Some ultraviolet transition frequencies in antiprotonic helium atoms were measured by sub-Doppler two-photon laser spectroscopy to a precision of 2.3-5 parts in 109. By comparing the results with
Precision laser spectroscopy experiments on antiprotonic helium
At CERN‘s Antiproton Decelerator (AD) facility, the Atomic Spectroscopyand Collisions Using Slow Antiprotons (ASACUSA) collaboration is carrying out precise laser spectroscopy experiments on
High-resolution laser resonances of antiprotonic helium in superfluid 4He
When atoms are placed into liquids, their optical spectral lines corresponding to the electronic transitions are greatly broadened compared to those of single, isolated atoms. This linewidth increase
Precision measurement of the mass difference between light nuclei and anti-matter counterparts
In ultra relativistic heavy-ion collisions a large and similar amount of nuclei and anti-nuclei is produced in the central pseudorapidity region allowing one to thoroughly investigate their
Laser spectroscopy of pionic helium atoms
TLDR
Long-lived pionic helium atoms (composed of a helium-4 nucleus, an electron and a negatively charged pion) are synthesized in a superfluid-helium target, as confirmed by laser spectroscopy involving the pion-occupied orbitals.
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