arXiv subjects

Y. Oki

Publications and source records attributed to Y. Oki.

5 recordsLinked to original sources

arXiv2015

7Be Solar Neutrino Measurement with KamLAND

We report a measurement of the neutrino-electron elastic scattering rate of 862 keV 7Be solar neutrinos based on a 165.4 kton-day exposure of KamLAND. The observed rate is 582 +/- 90 (kton-day)^-1, which corresponds to a 862 keV 7Be solar neutrino flux of (3.26 +/- 0.50) x 10^9 cm^-2s^-1, assuming a pure electron flavor flux. Comparing this flux with the standard solar model prediction and further assuming three flavor mixing, a nu_e survival probability of 0.66 +/- 0.14 is determined from the KamLAND data. Utilizing a global three flavor oscillation analysis, we obtain a total 7Be solar neutrino flux of (5.82 +/- 0.98) x 10^9 cm^-2s^-1, which is consistent with the standard solar model predictions.

hep-ex↗

arXiv2015

Study of electron anti-neutrinos associated with gamma-ray bursts using KamLAND

We search for electron anti-neutrinos ($\overlineν_e$) from long and short-duration gamma-ray bursts~(GRBs) using data taken by the KamLAND detector from August 2002 to June 2013. No statistically significant excess over the background level is found. We place the tightest upper limits on $\overlineν_e$ fluence from GRBs below 7 MeV and place first constraints on the relation between $\overlineν_e$ luminosity and effective temperature.

astro-ph.HE↗

arXiv2014

CeLAND: search for a 4th light neutrino state with a 3 PBq 144Ce-144Pr electron antineutrino generator in KamLAND

The reactor neutrino and gallium anomalies can be tested with a 3-4 PBq (75-100 kCi scale) 144Ce-144Pr antineutrino beta-source deployed at the center or next to a large low-background liquid scintillator detector. The antineutrino generator will be produced by the Russian reprocessing plant PA Mayak as early as 2014, transported to Japan, and deployed in the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND) as early as 2015. KamLAND's 13 m diameter target volume provides a suitable environment to measure the energy and position dependence of the detected neutrino flux. A characteristic oscillation pattern would be visible for a baseline of about 10 m or less, providing a very clean signal of neutrino disappearance into a yet-unknown, sterile neutrino state. This will provide a comprehensive test of the electron dissaperance neutrino anomalies and could lead to the discovery of a 4th neutrino state for Delta_m^2 > 0.1 eV^2 and sin^2(2theta) > 0.05.

physics.ins-det↗

arXiv2013

White paper: CeLAND - Investigation of the reactor antineutrino anomaly with an intense 144Ce-144Pr antineutrino source in KamLAND

We propose to test for short baseline neutrino oscillations, implied by the recent reevaluation of the reactor antineutrino flux and by anomalous results from the gallium solar neutrino detectors. The test will consist of producing a 75 kCi 144Ce - 144Pr antineutrino source to be deployed in the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND). KamLAND's 13m diameter target volume provides a suitable environment to measure energy and position dependence of the detected neutrino flux. A characteristic oscillation pattern would be visible for a baseline of about 10 m or less, providing a very clean signal of neutrino disappearance into a yet-unknown, "sterile" state. Such a measurement will be free of any reactor-related uncertainties. After 1.5 years of data taking the Reactor Antineutrino Anomaly parameter space will be tested at > 95% C.L.

hep-ex↗

arXiv2004

Flow characteristics and gelatinization kinetics of rice starch under strong alkali conditions

The normality dependence and the kinetics of flow behavior in the rice starch dispersion under strong alkali conditions were studied. Non-Newtonian flow (power-law) quantities n and μ(σ=μ(\dotε)^n; σ: shear stress, \dotε: shear rate) of the samples stored (gelatinized) at 20^{\circ}C for 10min after the addition of NaOH solution with the normality 0.090 - 0.175N, were measured by a cone-plate type rotational viscometer. For the flow analysis a care was taken for the ambiguity of the analysis range of flow data. The samples added with 0.14 - 0.16N NaOH displayed an apparently dilatant flow. As the normality of added NaOH increased, apparent viscosity η_a was steeply enhanced in the vicinity of 0.14N and started to grow almost exponentially. Next, the storage time dependence of flow properties was investigated for samples gelatinized for 6<t[min]<230 after the addition of 0.146N NaOH solution. A Newtonian analysis of the flow (σ- \dotε) data indicated that viscosity ηincreased exponentially in the early stage (6<t<35) and did linearly in the middle. It was argued that the observed time dependence of viscosity could be described by a first-order reaction hypothesis combined with the fluidity (η^{-1}) mixing rule with respect to ungelatinized and gelatinized fractions of starch. The application of this theoretical treatment to the present data suggested that the gelatinization process was composed of plural phases with different values of a rate constant. For the observed kinetic characteristic of alkali gelatinization, the discussions were presented on the basis of amylose complex formation.

physics.bio-ph↗