Experiment for the first direct measurement of the hyperfine splitting of positronium

A. Miyazaki, T. Suehara, A. Ishida, T. Namba, S. Asai, T. Kobayashi, H. Saito, M. Yoshida, T. Idehara, I. Ogawa, Y. Urushizaki, S. Sabchevski

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3 Citations (Scopus)


Positronium is an ideal system for the research of the bound state QED. The hyperfine splitting of positronium (Ps-HFS: about 203 GHz) is a good tool to test QED and also sensitive to new physics beyond the Standard Model via a quantum oscillation between an ortho-Ps and a virtual photon. Previous experimental results show 3.9 σ (15 ppm) discrepancy from the QED calculation. All previous experiments used an indirect method with static magnetic field to cause Zeeman splitting (a few GHz) between triplet states of ortho-Ps, from which the HFS value was derived. One possible systematic error source of the indirect method is non-uniformity of the static magnetic field. We are developing a new direct Ps-HFS measurement system without static magnetic field. In this measurement we use a gyrotron, a novel sub-THz light source, with a high-finesse Fabry-Pérot cavity to obtain enough radiation power at 203 GHz. The present status of the optimization studies and current design of the experiment are described.

Original languageEnglish
Article number012037
JournalJournal of Physics: Conference Series
Publication statusPublished - 2010
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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