CERN Accelerating science

Published Articles
Title	Laser spectroscopy of antiprotonic helium, and the antiproton-to-electron mass ratio measured by ASACUSA
Author(s)	Hori, M (Garching, Max Planck Inst.)
Publication	2017
Number of pages	6
In:	52nd Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 18 - 25 Mar 2017, pp.103-108
Subject category	Physics in General
Accelerator/Facility, Experiment	CERN ASACUSA
Abstract	The Atomic Spectroscopy and Collisions Using Slow Antprotons (ASACUSA) collaboration at CERN's Antiproton Decelerator is carrying out laser spectroscopy experiments to measure the atomic transition frequencies of antiprotonic helium ($\bar{p}He^+$). Techniques such as sub-Doppler two-photon laser spectroscopy and buffer-gas cooling of pHe + to cryogenic temperature $T =1.5–1.7 \text{K}$ are employed to measure the frequencies to a precision of $2.5$ parts in $10^9$. By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was determined as $M_{\bar{p}}/m_e = 1836.1526734(15)$. This agreed with the known proton-to-electron mass ratio at a precision of $8$ parts in $10^{10}$.

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