Precise laser spectroscopy of antiprotonic helium at CERN’s Antiproton Decelerator

Abstract

The ASACUSA collaboration of CERN has carried out several laser spectroscopy experiments of antiprotonic helium atoms. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was determined as M p /m e = 1836.152674(5). We are now developing some laser systems and detectors to further improve the experimental precision.

Atomic physics techniques for studying nuclear ground state properties, fundamental interactions and symmetries: status and perspectives

“…The ALPHA (former ATHENA) [222,223], ASACUSA [224][225][226], and ATRAP [227][228][229] collaborations started at the antiproton decelerator (AD) at CERN a program to test CPT invariance by comparing the hyperfine splitting in the ground state (ASACUSA) or the 1s-2s transition frequency (ALPHA and ATRAP) of hydrogen with those of antihydrogen. Very recently, a forth collaboration, AEGIS, is preparing a new experiment for comparing the fall of hydrogen with that of antihydrogen in the gravitational field of the earth [230].…”

“…The laser spectroscopic investigations of antiprotonic helium by the ASACUSA Collaboration were presented by Masaki Hori. These experiments, in combination with very accurate three-body QED calculations, resulted in a new measurement of the antiproton-to-electron mass ratio with a relative uncertainty of 2 · 10 −9 [226].…”