arXiv subjects

S. Shimizu

Publications and source records attributed to S. Shimizu.

22 records · Page 2Linked to original sources

arXiv2004

A new limit of T-violating transverse muon polarization in the $K^{+}\toπ^{0}μ^{+} ν$ decay

A search for T-violating transverse muon polarization ($P_T$) in the $K^{+}\to π^{0}μ^{+}ν$ decay was performed using kaon decays at rest. A new improved value, $P_T= -0.0017\pm 0.0023 (stat)\pm 0.0011 (syst)$, was obtained giving an upper limit, $| P_T | < 0.0050$. The T-violation parameter was determined to be Im$ξ= -0.0053 \pm 0.0071(stat)\pm 0.0036(syst)$ giving an upper limit, $|$Im$ξ| <0.016$.

hep-ex↗

arXiv2004

GPM Ground Validation Basic Radar Products and Implications for Observation Strategies

Recommendations are made for NASA/JAXA Global Precipitation Measurement (GPM) satellite Ground Validation (GV) program. This report details recommended GV site local radar products based on data from surface-based scanning radars including S-band, C-band, and X-band polarimetric and non-polarimetric radars. Three general categories of products are described: text products summarizing information on the statistical characteristics of the radar data and derived parameters, 2D products providing maps of the horizontal variability of near surface radar observed and derived parameters, and 3D products describing volumetric echo structure. Regional composites could include products based on several of the 2D and 3D single radar products. Several types of time-integrated 2D and 3D products are also recommended. A brief discussion of useful ancillary data from other sources and remaining challenges concludes the report.

physics.ao-ph↗

arXiv2002

High TC ferromagnetism in diluted magnetic semiconducting GaN:Mn films

Wurtzite GaN:Mn films on sapphire substrates were successfully grown by use of the molecular beam epitaxy (MBE) system. The film has an extremely high Curie temperature of around 940 K, although the Mn concentration is only about 3 ~ 5 %. Magnetization measurements were carried out in magnetic fields parallel to the film surface up to 7 T. The magnetization process shows the coexistence of ferromagnetic and paramagnetic contributions at low temperatures, while the typical ferromagnetic magnetization process is mainly observed at high temperatures because of the decrease of the paramagnetic contributions. The observed transport characteristics show a close relation between the magnetism and the impurity conduction. The double exchange mechanism of the Mn-impurity band is one of the possible models for the high-TC ferromagnetism in GaN:Mn.

cond-mat.mtrl-sci↗

arXiv2001

Molecular Beam Epitaxy of Wurtzite (Ga,Mn)N Films on Sapphire(0001) Showing the Ferromagnetic Behaviour at Room Temperature

Wurtzite (Ga,Mn)N films showing ferromagnetic behaviour at room temperature were successfully grown on sapphire(0001) substrates by molecular beam epitaxy using ammonia as nitrogen source. Magnetization measurements were carried out by a superconducting quantum interference device at the temperatures between 1.8K and 300K with magnetic field applied parallel to the film plane up to 7T. The magnetic-field dependence of magnetization of a (Ga,Mn)N film at 300K were ferromagnetic, while a GaN film showed Pauli paramagnetism like behaviour. The Curie temperatures of a (Ga,Mn)N film was estimated as 940K.

cond-mat.mtrl-sci↗