Measurement of the proton Zemach radius from the hyperfine splitting in muonic hydrogen atom

Sohtaro Kanda, Katsuhiko Ishida, Masahiko Iwasaki, Yue Ma, Shinji Okada, Aiko Takamine, Hideki Ueno, Katsumi Midorikawa, Norihito Saito, Satoshi Wada, Masaki Yumoto, Yu Oishi, Masaharu Sato, Shuu Aikawa, Kazuo S. Tanaka, Yasuyuki Matsuda

Research output: Contribution to journalConference articlepeer-review

6 Citations (Scopus)


Muonic hydrogen is a bound state of a proton and a negative muon. Its Bohr radius is 200 times smaller than that of an electronic hydrogen atom. Therefore, a spectroscopy of the muonic hydrogen is highly sensitive to the finite size effect of proton. Recent years, the proton charge radius was determined by the laser spectroscopy of the Lamb shifts in muonic hydrogen atom. The experiment determined the proton charge radius significantly smaller than the results of past measurements. This anomaly is called "proton radius puzzle" and it has been an important unsolved problem in subatomic physics. Towards solving the puzzle, a new measurement of the ground-state hyperfine splitting in muonic hydrogen was proposed. The hyperfine splitting of muonic hydrogen derives the proton Zemach radius, which is defined as a convolution of the charge distribution with the magnetic moment distribution. This experiment aims to determine the proton Zemach radius with 1% precision by a measurement of the decay electron angular asymmetry. In order to test the feasibility of the laser spectroscopy, a preliminary experiment to measure the hyperfine quenching rate was proposed.

Original languageEnglish
Article number012009
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 2018 Dec 21
Event10th International Conference on Precision Physics of Simple Atomic Systems, PSAS 2018 - Vienna, Austria
Duration: 2018 May 142018 May 18

ASJC Scopus subject areas

  • Physics and Astronomy(all)


Dive into the research topics of 'Measurement of the proton Zemach radius from the hyperfine splitting in muonic hydrogen atom'. Together they form a unique fingerprint.

Cite this