Jul 22 – 26, 2019
Europe/Rome timezone

X-ray spectroscopy of muonic atoms isolated in vacuum using transition edge sensors

Jul 25, 2019, 5:45 PM
1h 15m
Piazza Città di Lombardia (Milano)

Piazza Città di Lombardia


Piazza Città di Lombardia, 1, 20124 Milano MI
Poster Low Temperature Detector Applications Poster session


Dr Shinji Okada (RIKEN)


High-resolution X-ray spectroscopy of highly-charged muonic atoms/ions isolated in vacuum is an ideal probe to explore quantum electrodynamics (QED) effects. One of the major topic in fundamental atomic physics is to conduct these experiments in high-Z atom in which the bound particles experience extremely strong electric fields.
A negatively-charged muon can bind to a nucleus via the Coulomb field. This “muonic atom” is essentially hydrogen-like in its electronic structure. Since a muon is 200 times more massive than an electron, a muonic atom has a Bohr radius 200 times smaller than that of atomic hydrogen. This allows to test QED in strong field in a very different regime, since at such short distances the dominant QED contribution is the vacuum polarization, while it is the self-energy in highly-charged ions. After a negatively-charged muon is captured by the nucleus in a highly excited state, the muon peels off most (or all) of the electrons bound to the nucleus as Auger electrons, and thereby generating highly-charged muonic atoms in vacuum.
While a low-density target is required to avoid rapid refilling of electrons into the highly charged muonic atom from the surrounding atoms, it is experimentally difficult to efficiently stop muons in a low-density target. This is due to their large momentum distribution via traveling pion decay, resulting in insufficient x-ray yields with the conventional high-resolution x-ray spectroscopy technology based on diffraction from Bragg crystals, unless one uses a device like the PSI cyclotron trap.
We aim to realize the high-resolution muonic atom X-ray spectroscopy with low-density gas target with a combination of the world highest intensity pulsed negative muon beam at J-PARC MLF MUSE (Tokai, Japan) and an X-ray spectrometer based on a 240 pixel array of superconducting transition-edge-sensor (TES) microcalorimeters.
In April 2019 we will perform a feasibility test at J-PARC and report the outcome of these new result.

Less than 5 years of experience since completion of Ph.D N
Student (Ph.D., M.Sc. or B.Sc.) N

Primary author

Dr Shinji Okada (RIKEN)


Carl Reintsema (NIST) Daniel Schmidt (NIST) Daniel Swetz (NIST) Dr Douglas Bennett (NIST) Galen O’Neil (NIST) Gene Hilton (NIST-Boulder) Hideyuki Tatsuno Dr Hirofumi NODA (Osaka University) Joel Ullom (NIST/University of Colorado) Johnathon Gard (NIST) Joseph Fowler (NIST) Dr Kazuhiko Ninomiya (Osaka University) Dr Kelsey Morgan (NIST) Prof. Kouichiro Shimomura (KEK) Dr Malcolm Durkin (NIST) Dr Miho Katsuragawa (IPMU) Dr Naritoshi Kawamura (KEK) Prof. Paul Indelicato (CNRS) Dr Pietro Caradonna (IPMU) Ryota Hayakawa (Tokyo Metropolitan University) Dr Shin Watanabe (JAXA) Dr Shinichiro Takeda (IPMU) Shinya Yamada (Tokyo Metropolitan University) Dr Sohtaro Kanda (RIKEN) Dr Soshi Takeshita (KEK) Tadaaki Isobe (RIKEN) Tadashi Hashimoto (Japan Atomic Energy Agency) Prof. Tadayuki Takahashi (IPMU) Dr Takuma Okumura (RIKEN) Toshiyuki Azuma (RIKEN) W. Bertrand (Randy) Doriese (NIST) Prof. Yasuhiro Miyake (KEK) Dr Yasuhiro Ueno (RIKEN) Prof. Yasushi Kino (Tohoku University) Dr Yuto Ichinohe (Rikkyo University)

Presentation materials