Search Results (7 total)

A general approach is outlined to predict the chemical compositions of solute nanoclusters embedded in materials with nearly free electrons. Based on the experimental results of the two-dimensional angular correlation of positron annihilation radiation and the corresponding theoretical calculations, we show that the Fermi surface (FS)–Brillouin zone interaction is a key to understand the chemical composition realized in solute nanoclusters because the presence of FS necks at zone boundaries causes a reduction in electron energy due to the band-gap effect.

A single rf bunch in the KEK proton synchrotron was accelerated with an induction acceleration method from the injection energy of 500 MeV to 5 GeV.

Positron two-dimensional angular correlation of annihilation radiation (2D ACAR), i.e., the 2D projection of the electron momentum densities sampled by positron, in Si is employed to verify the prediction of the density functional theory within the local-density approximation (LDA). Carefully conducted test shows that the LDA introduces small but definite discrepancies to the 2D-ACAR anisotropies. Self-energy calculation using the GW method indicates that density-fluctuation contributes anisotropic momentum-density correction and thus improves the agreement between theory and experiment. These results provide valuable annotations to the arguments concerning the accuracy and validity of the LDA and GW schemes.

An e^-p instability has been observed in some proton rings. The instability, which causes beam loss, limits the performance of the ring. The instability may be serious for 3 and 50 GeV proton storage rings in the Japan Proton Accelerator Research Complex (J-PARC). We study the e^-p instability in several high intensity proton storage rings operated in the world. This work informs J-PARC of the necessity to cure the instability, for example, by applying a TiN coating on the chamber surface.

We have measured the inclusive D^*± production cross secton in a two-photon collision at the KEK e⁺e^- collider TRISTAN. The mean √s of the collider was 57.16 GeV and the integrated luminosity was 150 pb^-1. The differential cross section [dσ(D^*±)/dP_T] was obtained in the P_T range between 1.6 and 6.6 GeV and compared with theoretical predictions, such as those involving direct and resolved photon processes.

The momentum dependence of the analyzing power A_y in proton-proton elastic scattering has been measured in small steps using an internal target during polarized beam acceleration from 1 to 3 GeV/c. The momentum bin size ranges from 5 to 18 MeV/c. The relative uncertainty of A_y is typically less than 0.01 for each momentum bin. Narrow structures have been found in the two-proton invariant mass distribution of A_y.