Muon

Professor Hideki Yukawa predicted the existence of pions in 1935, and Professor Yoshio Nishina discovered muons in cosmic rays in 1937. Nowadays, pions and muons can be artificially produced with high-energy proton accelerators. In the nuclear reactions by injecting high-energy proton beam into carbon nuclei, pions are generated, and then muos are created by the decay of pions

Muons are classified to electron group in elementary particles, and have the mass of 1/9 of proton mass and of 207 times of electron mass. Therefore positive muons behave like "light proton" and negative muons do like " heavy electron" in materials.

Positive muons have their own spins (magnet needle) with 100% polarization, and can detect very precisely local magnetic fields and the fluctuations. The method to study characteristic of materials by observing the time dependent change of muon spin polarization is called "Muon Spin Rotation, Relaxation and Resonance(μSR method), and is applied to condensed matter studies of newly fabricated materials.

Negative muons are captured into orbits of nuclei, and form "Muonic Atoms" with the atomic size of 1/207 compared with ordinary atoms. At the formation of muonic atoms, characteristic muoncic X-rays are emitted with higher energies by 207 times compared with X-rays from ordinary atoms. By applying unique features, muon catalyzed d-t fusion, nuclear physic study on nuclear charge density distributions and application to non-destructive analysis are in progress.