Showing papers by "Shoji Yamamoto published in 2004"
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, Chonnam National University6, George Mason University7, Gifu University8, Indiana University9, Kobe University10, Kyoto University11, Los Alamos National Laboratory12, Louisiana State University13, University of Maryland, College Park14, Massachusetts Institute of Technology15, University of Minnesota16, Miyagi University of Education17, Stony Brook University18, Nagoya University19, Niigata University20, Osaka University21, Seoul National University22, Shizuoka University23, Sungkyunkwan University24, Tohoku University25, Tokai University26, Tokyo Institute of Technology27, University of Warsaw28, University of Washington29
TL;DR: A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation, which constrained nu(micro)<-->nu(tau) neutrinos oscillation parameters.
Abstract: Muon neutrino disappearance probability as a function of neutrino flight length $L$ over neutrino energy $E$ was studied. A dip in the $L/E$ distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed $L/E$ distribution constrained ${\ensuremath{
u}}_{\ensuremath{\mu}}\ensuremath{\leftrightarrow}{\ensuremath{
u}}_{\ensuremath{\tau}}$ neutrino oscillation parameters; $1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}l\ensuremath{\Delta}{m}^{2}l3.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{e}\mathrm{V}}^{2}$ and ${sin }^{2}2\ensuremath{\theta}g0.90$ at 90% confidence level.
522 citations
Boston University1, University of Tokyo2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, Chonnam National University6, George Mason University7, Gifu University8, Indiana University9, Kobe University10, Kyoto University11, Los Alamos National Laboratory12, Louisiana State University13, University of Maryland, College Park14, Massachusetts Institute of Technology15, University of Minnesota16, Stony Brook University17, Nagoya University18, Niigata University19, Osaka University20, Seoul National University21, Shizuoka University22, Sungkyunkwan University23, Tohoku University24, Tokai University25, Tokyo Institute of Technology26, University of Warsaw27, University of Washington28
TL;DR: The results of indirect searches for Weakly Interacting Massive Particles (WIMPs) with 1679.6 live days of data from the Super-Kamiokande detector using neutrino-induced upward through-going muons are presented in this paper.
Abstract: We present the results of indirect searches for Weakly Interacting Massive Particles (WIMPs), with 1679.6 live days of data from the Super-Kamiokande detector using neutrino-induced upward through-going muons. The search is performed by looking for an excess of high energy muon neutrinos from WIMP annihilations in the Sun, the core of the Earth, and the Galactic Center, as compared to the number expected from the atmospheric neutrino background. No statistically significant excess was seen. We calculate the flux limits in various angular cones around each of the above celestial objects. We obtain conservative model-independent upper limits on the WIMP-nucleon cross section as a function of WIMP mass, and compare these results with the corresponding results from direct dark matter detection experiments.
323 citations
University of California, Irvine1, University of Tokyo2, Boston University3, Harvard University4, California State University5, Chonnam National University6, George Mason University7, Gifu University8, University of Hawaii at Manoa9, University of Chicago10, Kobe University11, Kyoto University12, Los Alamos National Laboratory13, Louisiana State University14, University of Maryland, College Park15, Massachusetts Institute of Technology16, University of Minnesota17, Stony Brook University18, University of Utah19, Brookhaven National Laboratory20, Nagoya University21, Niigata University22, Osaka University23, Seoul National University24, Shizuoka University25, Sungkyunkwan University26, Tohoku University27, Tokai University28, Tokyo Institute of Technology29, University of Warsaw30, University of Washington31
TL;DR: In this article, the effect of neutrino oscillation on the shapes of energy spectra was considered and a limit of micro(nu) = 3.6x10(-10))micro(B) at 90% C.L. was obtained.
Abstract: A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)
84 citations
Seoul National University1, Kobe University2, University of Tokyo3, University of Washington4, University of California, Irvine5, Chonnam National University6, Miyagi University of Education7, Kyoto University8, Tohoku University9, Stony Brook University10, Okayama University11, Boston University12, University of Warsaw13, Korea University14, Niigata University15, Dongshin University16, Massachusetts Institute of Technology17, Tokyo University of Science18, Osaka University19
TL;DR: A search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrINO experiment is presented and one candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target.
Abstract: We present a search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+/-0.6 events and is dominated by misidentification of events from neutral current pi(0) production. We exclude the nu(micro) to nu(e) oscillations at 90% C.L. for the effective mixing angle in the 2-flavor approximation of sin((2)2theta(microe)( approximately 1/2sin((2)2theta(13))>0.15 at Deltam(2)(microe)=2.8 x 10(-3) eV(2), the best-fit value of the nu(micro) disappearance analysis in K2K. The most stringent limit of sin((2)2theta(microe)<0.09 is obtained at Deltam(2)(microe)=6 x 10(-3) eV(2).
64 citations
TL;DR: In this article, a comparative study of bosonic languages to describe one-dimensional Heisenberg ferrimagnets is presented, and a modified spin-wave scheme, which introduces a Lagrange multiplier keeping the native energy structure free from temperature and thus differs from the original Takahashi scheme, is particularly stressed as a useful tool to investigate onedimensional quantum ferrimagnetism.
Abstract: We present a comparative study of bosonic languages to describe one-dimensional Heisenberg ferrimagnets. The ferrimagnetic Schwinger-boson mean-field theory demonstrated by Wu et al., the antiferromagnetic modified spin-wave theory designed by Takahashi, and its ferrimagnetic variant proposed by Yamamoto et al. are employed to calculate the energy structure and the thermodynamics of various ferrimagnets. A modified spin-wave scheme, which introduces a Lagrange multiplier keeping the native energy structure free from temperature and thus differs from the original Takahashi scheme, is particularly stressed as a useful tool to investigate one-dimensional quantum ferrimagnetism. The antiferromagnetic limit of these descriptions is also considered.
40 citations
TL;DR: Fujiwara et al. as mentioned in this paper studied the instability of the toroidicity-induced Alfven eigenmodes and their destabilization by energetic ions in stellarators, mainly in the Large Helical Device (LHD) [M. I. Kolesnichenko et al., Nucl. Fusion 41, 1355 (2001)] plasmas.
Abstract: Alfven eigenmodes and their destabilization by energetic ions in stellarators, mainly, in the Large Helical Device (LHD) [M. Fujiwara, K. Kawahata, N. Ohyabu et al., Nucl. Fusion 41, 1355 (2001)] plasmas, are considered. A general expression for the instability growth rate is derived, which generalizes that obtained by Ya. I. Kolesnichenko et al. [Phys. Plasmas 9, 517 (2002)] by taking into account the finite magnitude of the perturbed longitudinal magnetic field. The structures of the Alfven continuum and Alfven eigenmodes, as well as the resonances of the wave–particle interaction, are studied. A numerical simulation of the destabilization of Alfven waves with low mode numbers during neutral-beam injection in a particular LHD shot is carried out. The obtained solutions represent even and odd core-localized toroidicity-induced Alfven eigenmodes, the calculated frequencies and the mode numbers being in agreement with experimental data. The growth rates of the instabilities are calculated.Alfven eigenmodes and their destabilization by energetic ions in stellarators, mainly, in the Large Helical Device (LHD) [M. Fujiwara, K. Kawahata, N. Ohyabu et al., Nucl. Fusion 41, 1355 (2001)] plasmas, are considered. A general expression for the instability growth rate is derived, which generalizes that obtained by Ya. I. Kolesnichenko et al. [Phys. Plasmas 9, 517 (2002)] by taking into account the finite magnitude of the perturbed longitudinal magnetic field. The structures of the Alfven continuum and Alfven eigenmodes, as well as the resonances of the wave–particle interaction, are studied. A numerical simulation of the destabilization of Alfven waves with low mode numbers during neutral-beam injection in a particular LHD shot is carried out. The obtained solutions represent even and odd core-localized toroidicity-induced Alfven eigenmodes, the calculated frequencies and the mode numbers being in agreement with experimental data. The growth rates of the instabilities are calculated.
29 citations
National Institutes of Natural Sciences, Japan1, Hokkaido University2, Nagoya University3, University of Tsukuba4, Kyushu University5, University of Tokyo6, Graduate University for Advanced Studies7, Kyoto University8, Oak Ridge National Laboratory9, Tohoku University10, Japan Atomic Energy Agency11
TL;DR: In this article, the authors reviewed the recent progress in the Large Helical Device (LHD) experiment during the last two years and reviewed its operational regime toward fusion-relevant conditions while taking advantage of the netcurrent-free heliotron concept employing a superconducting coil system.
Abstract: Recent progress in the Large Helical Device (LHD) experiment during the last 2 yr is reviewed The LHD has been extending its operational regime toward fusion-relevant conditions while taking advantage of the net-current-free heliotron concept employing a superconducting coil system Heating capability has exceeded 10 MW, and the central ion and electron temperatures have reached 7 and 10 keV, respectively The maximum values of beta and pulse length have been extended to 32% and 150 s, respectively Several encouraging physics observations have been obtained, ie, simultaneous achievement of the mitigation of the magnetohydrodynamic instability criteria and good confinement, and formation of an internal transport barrier The initial results have been obtained using a local island divertor, which shows the possibility of particle control at the plasma edge
15 citations
TL;DR: In this article, the H-mode transition properties of ECH plasmas in Heliotron J have been studied with special reference to their magnetic configuration dependences, such as the edge iota dependences.
Abstract: The H-mode transition properties of 70-GHz, 0.4-MW electron cyclotron heating (ECH) plasmas in Heliotron J have been studied with special reference to their magnetic configuration dependences, such as the edge iota dependences. Two edge iota windows for the H-mode transition were observed to be (a) 0.54 < ι`(a)/2π < 0.56 in separatrix discharge plasmas and (b) 0.62 < ι`(a)/2π < 0.63 in partial wall-limiter discharge plasmas if a certain threshold line-averaged electron density (n e =1.2-1.6 × 10 19 m -3 ) is achieved, where ι`(a) is the vacuum edge iota value and a is the plasma minor radius, respectively. A strong dependence of the quality of the H-mode on the edge topology conditions was revealed. The energy confinement time for the separatrix discharge plasmas was found to be enhanced beyond the normal ISS95 scaling in the transient H-mode phase, being 50% longer than that in the before transition phase. The window characteristics are discussed on the basis of the calculated geometrical poloidal viscous damping rate coefficient in a collisional plasma, indicating that the behavior of the viscous damping rate coefficient alone could not explain the observed characteristics. The bootstrap current properties of ECH plasmas and the relevant electron cyclotron current drive experimental results are also discussed.
14 citations
TL;DR: In terms of spinless fermions via the Jordan-Wigner transformation along a snakelike path and spin waves modified so as to restore the sublattice symmetry, this paper investigated the static and dynamic pro...
Abstract: In terms of spinless fermions via the Jordan–Wigner transformation along a snakelike path and spin waves modified so as to restore the sublattice symmetry, we investigate the static and dynamic pro...
9 citations
TL;DR: In this article, the optical conductivity for solitonic excitations in halogen-bridged binuclear metal $(MMX)$ complexes was investigated using the one-dimensional single-band extended Peierls-Hubbard model.
Abstract: Employing the one-dimensional single-band extended Peierls-Hubbard model, we investigate optical conductivity for solitonic excitations in halogen-bridged binuclear metal $(MMX)$ complexes. Photoinduced soliton absorption spectra for $MMX$ chains possibly split into two bands, forming a striking contrast to those for conventional mononuclear metal $(MX)$ analogs, due to the broken electron-hole symmetry combined with relevant Coulomb and∕or electron-phonon interactions.
8 citations
TL;DR: In this article, the nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is studied in terms of a modified spin-wave theory and the second-order process is considered.
Abstract: Nuclear spin–lattice relaxation in one-dimensional Heisenberg ferrimagnets is studied in terms of a modified spin-wave theory. We consider the second-order process, where a nuclear spin flip induces virtual spin waves which are then scattered thermally via the four-magnon exchange interaction, as well as the first-order process, where a nuclear spin directly interacts with spin waves via the hyperfine interaction. We point out a possibility of the three-magnon relaxation process predominating over the Raman one and suggest model experiments.
TL;DR: In this paper, the optical conductivity of photogenerated solitons in quasi-one-dimensional halogen-bridged binuclear metal (MMX) complexes is investigated with particular emphasis on a comparison between the two family compounds R_4_[Pt_2_(P_2_O_5_H_2 )_4X]nH 2
Abstract: The optical conductivity of photogenerated solitons in quasi-one-dimensional halogen-bridged binuclear metal (MMX) complexes is investigated with particular emphasis on a comparison between the two family compounds R_4_[Pt_2_(P_2_O_5_H_2_)_4_X]nH_2_O (X=Cl,Br,I;R=NH_4_,Na,K,...; pop=diphosphonate=P_2_O_5_H_2_^2-^) and Pt_2_(dta)_4_I (dta=dithioacetate=CH_3_CS_2_^-^). Soliton-induced absorption spectra for the pop complexes should split into two bands, while those for the dta complex should consist of a single band.
TL;DR: In this paper, a new theory is proposed to interpret nuclear spin-lattice relaxation-time (T 1 ) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C 2 H 8 N 2 ) 2 NO 2 (ClO 4 ) (NENP).
Abstract: A new theory is proposed to interpret nuclear spin–lattice relaxation-time ( T 1 ) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C 2 H 8 N 2 ) 2 NO 2 (ClO 4 ) (NENP). While Sagi and Affleck [Phys. Rev. B 53 (1996) 9188] pioneeringly discussed this subject in terms of field-theoretical languages, there is no theoretical attempt yet to explicitly simulate the novel observations of T 1 -1 reported by Fujiwara et al. [Phys. Rev. B 47 (1993) 11860]. By means of modified spin waves, we interpret the minimum of T 1 -1 as a function of an applied field , pending for the past decade.
TL;DR: In this paper, it was shown that the major contribution to 1/T 1 being made by the three-magnon scattering rather than the Raman scattering was made by a three-dimensional spin-wave theory.
Abstract: Recent proton spin–lattice relaxation-time (T1) measurements on the ferrimagnetic chain compound NiCu(C7H6N2O6)(H2O)3·2H2O are explained by an elaborately modified spin-wave theory. We give strong evidence of the major contribution to 1/T1 being made by the three-magnon scattering rather than the Raman scattering.
TL;DR: In this paper, a modified spin-wave theory was proposed to study the nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets by means of modified spinwave theory.
Abstract: Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is studied by means of a modified spin-wave theory. We consider the second-order process, where a nuclear spin flip induces virtual spin waves which are then scattered thermally via the four-magnon exchange interaction, as well as the first-order process, where a nuclear spin directly interacts with spin waves via the hyperfine interaction. We point out a possibility of the three-magnon relaxation process predominating over the Raman one and suggest model experiments.
TL;DR: In this article, a new theory is proposed to interpret nuclear spin-lattice relaxation-time (T_1_) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C_2H_8_N_2_)_2.NO_2_(ClO_4_) (NENP).
Abstract: A new theory is proposed to interpret nuclear spin-lattice relaxation-time (T_1_) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C_2_H_8_N_2_)_2_NO_2_(ClO_4_) (NENP). While Sagi and Affleck pioneeringly discussed this subject in terms of field-theoretical languages, there is no theoretical attempt yet to explicitly simulate the novel observations of 1/T_1_ reported by Fujiwara et al.. By means of modified spin waves, we solve the minimum of 1/T_1_ as a function of an applied field, pending for the past decade.
TL;DR: In this article, the authors give a strong evidence that the major contribution to 1/T_1_ being made by the three-magnon scattering rather than the Raman one is made.
Abstract: Recent proton spin-lattice relaxation-time (T_1_) measurements on the ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O are explained by an elaborately modified spin-wave theory. We give a strong evidence of the major contribution to 1/T_1_ being made by the three-magnon scattering rather than the Raman one.
TL;DR: In this article, the magnetic properties of the spin − 1 2 two-leg Heisenberg ladder antiferromagnet were investigated and two formulations of the Jordan-Wigner transformation along an elaborately ordered path were developed.