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Sato, T.

Publications and source records attributed to Sato, T..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

NEUTRINO EMISSIVITIES FROM DEUTERON BREAKUP AND FORMATION IN SUPERNOVAE

Neutrino emissions from electron/positron capture on the deuteron and the nucleon-nucleon fusion processes in a supernova core are studied. These weak processes are evaluated in an approach which consists of one-nucleon and two-nucleon meson-exchange currents and nuclear wave functions generated by a high precision nucleon-nucleon potential. In addition to the cross sections for these processes involving the deuteron, we present neutrino emissivities due to these processes calculated for typical profiles of core-collapsed supernovae. These novel neutrino emissivities are compared with the standard neutrino-emission mechanisms. We find that the electron-type neutrino emissivity due to electron capture on the deuteron is comparable to that on the proton in the deuteron abundant region. The electron-type antineutrino emissivity due to positron capture on the deuteron is much smaller than that on the neutron. The neutrino emissivity through deuteron formation is smaller than the conventional processes, but may be important in a situation where the nucleon-nucleon bremsstrahlung is important. The implications of the new channels involving deuterons for the supernova mechanism are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Search for heavy neutrinos in K + → μ + ν H decays

Here, evidence of a heavy neutrino, ν H , in the K + →μ + ν H decays was sought using the E949 experimental data with an exposure of 1.70 × 10 12 stopped kaons. With the major background from the radiative K + →μ + ν μ γ decay understood and suppressed, upper limits (90% C.L.) on the neutrino mixing matrix element between the muon and heavy neutrinos, |U μH | 2 , were set at the level of 10 –7 to 10 –9 for the heavy neutrino mass region 175 to 300 MeV/c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

THERMODYNAMICS OF THE COMA CLUSTER OUTSKIRTS

We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot ({approx}8 keV), dynamically active, non-cool core system, focusing on the thermodynamic properties of the intracluster medium on large scales. For azimuths not aligned with an infalling subcluster toward the southwest, our measured temperature and X-ray brightness profiles exhibit broadly consistent radial trends, with the temperature decreasing from about 8.5 keV at the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of our detection limit. The southwest merger significantly boosts the surface brightness, allowing us to detect X-ray emission out to {approx}2.2 Mpc along this direction. Apart from the southwestern infalling subcluster, the surface brightness profiles show multiple edges around radii of 30-40 arcmin. The azimuthally averaged temperature profile, as well as the deprojected density and pressure profiles, all show a sharp drop consistent with an outwardly-propagating shock front located at 40 arcmin, corresponding to the outermost edge of the giant radio halo observed at 352 MHz with the Westerbork Synthesis Radio Telescope. The shock front may be powering this radio emission. A clear entropy excess inside of r{sub 500} reflects the violent merging events linked with these morphological features. Beyond r{sub 500}, the entropy profiles of the Coma Cluster along the relatively relaxed directions are consistent with the power-law behavior expected from simple models of gravitational large-scale structure formation. The pressure is also in agreement at these radii with the expected values measured from Sunyaev-Zel'dovich data from the Planck satellite. However, due to the large uncertainties associated with the Coma Cluster measurements, we cannot yet exclude an entropy flattening in this system consistent with that seen in more relaxed cool core clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Development of U and Pu Co-Recovery Process (Co-Processing) for Future Reprocessing

Co-processing process, which is the modified Purex process focused on co-recovery of Pu and U, has been studied at Operation Testing Laboratory, Tokai Reprocessing Plant in JAEA. The set up of the process was performed with flow-sheets study by process calculation to avoid Pu isolation in the whole process and to co-recover Pu/U product solution with a suitable Pu/U ratio (0.5< Pu/U <2). The initial Pu/U ratios of the feed solutions were taken as 1%, 3% and 20% considering the composition of the future spent fuels. The verification of the flow-sheets for each feed solutions were carried out with mixer-setters and active Pu/U feed solutions, focusing on the partitioning unit, and favorable back extraction performances of Pu accompanied by U were observed at all cases of the given feed solutions. According to these results, the co-processing process showed a good prospect to treat all kinds of future fuels from LWR, LWR-MOX and FBR, and a good prospect to be simplified by omitting the Pu/U purification cycle.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2011

Study of the K 0 L →π⁰π⁰νν¯decay

The rare decay K 0 L →π⁰π⁰νν̄ was studied with the E391a detector at the KEK 12-GeV proton synchrotron. Based on 9.4×10⁹ K 0 L decays, an upper limit of 8.1×10⁻⁷ was obtained for the branching fraction at 90% confidence level. We also set a limit on the K 0 L →π⁰π⁰X (X→invisible particles) process; the limit on the branching fraction varied from 7.0×10⁻⁷ to 4.0×10⁻⁵ for the mass of X ranging from 50 MeV/c² to 200 MeV/c².

Ogata, R.↗
NASA NTRS1990

Global simulation of the solar wind-magnetosphere interaction - The importance of its numerical validity

This paper examines the global interaction of the solar wind with the geomagnetic field, using a newly developed three-dimensional high-precision MHD simulation code which employs the fourth-order Runge-Kutta-Gill scheme in time and the direct finite-difference method in space, and which allows much less numerical error than the conventional code. The simulation reveals in detail the formation processes of the magnetosphere and the bow shock, as well as the plasma sheet formation process. It is shown that, contrary to the conventional understanding, no Kelvin-Helmholtz instability occurs along the magnetopause in an ideal MHD.

Watanabe, K.↗
NASA NTRS1990

Studies of velocity fluctuations in the lower atmosphere using the MU radar. I - Azimuthal anisotropy. II - Momentum fluxes and energy densities

Results are presented from a six-day campaign to observe velocity fluctuations in the lower atmosphere using the MU radar (Fukao et al., 1985) in Shigaraki, Japan in March, 1986. Consideration is given to the azimuthal anisotropy, the frequency spectra, the vertical profiles of energy density, and the momentum flux of the motion field. It is found that all of the observed azimuthal variations are probably caused by a gravity wave field whose parameters vary with time. The results show significant differences between the mean zonal and meridional frequency spectra and different profiles of mean energy density with height for different frequency bands and for zonal and meridional components.

Vanzandt, T. E.↗