Laser spectroscopy of antiprotonic helium atoms at CERN’s new ELENA facility

• Applicant: Privatdozent Dr. Masaki Hori
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504822495

Metastable antiprotonic helium is a neutral three-body exotic atom that consists of a helium nucleus, an electron occupying the 1s state, and an antiproton in a Rydberg state of large principal (n=38) and orbital angular momentum (l=n-1) quantum numbers. We propose to utilize the unprecedented high-quality beam of the new ELENA facility of CERN and the latest laser metrology techniques to carry out sub-Doppler two-photon laser spectroscopy of narrow resonances of antiprotonic helium to ultimately a fractional precision of 10^-11 scale which is two orders of magnitude higher than in past experiments. This should then rival the best determinations of the proton-to-electron mass ratio from Penning trap and HD+ spectroscopy experiments and provide an important consistency test of the QED calculations, as well as a test of CPT symmetry. Upper limits on possible fifth forces between the antiproton and helium nucleus would then be obtained. For the first 3 years of this project, we intend to construct and validate an induction decelerator that reduces the energy of the antiproton beam provided by ELENA from 100 keV to <30 keV, and use the induction decelerator to optimize the laser spectroscopic signal of antiprotonic helium, and discover the narrow two-photon resonances of antiprotonic helium.

• DFG Programme: Research Grants
• International Connection: Bulgaria, Finland, Italy, Japan, Switzerland
• Cooperation Partners: Dr. Claudio Calosso; Dr. Andreas Dax; Professor Dr. Kai Nordlund; Dr. Boyan Obreshkov; Professor Chihiro Ohmori; Professorin Dr. Anna Soter; Professor Dr. Dage Sundholm, Ph.D.