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Search Results: 1 - 10 of 262005 matches for " B. K. Fujikawa "
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Half-Life of $^{14}$O
J. T. Burke,P. A. Vetter,S. J. Freedman,B. K. Fujikawa,W. T. Winter
Physics , 2006, DOI: 10.1103/PhysRevC.74.025501
Abstract: We have measured the half-life of $^{14}$O, a superallowed $(0^{+} \to 0^{+})$ $\beta$ decay isotope. The $^{14}$O was produced by the $^{12}$C($^{3}$He,n)$^{14}$O reaction using a carbon aerogel target. A low-energy ion beam of $^{14}$O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find $t_{1/2} = 70.696\pm 0.052$ s. This result is $1.5\sigma$ higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurement.
A geoneutrino experiment at Homestake
N. Tolich,Y. -D. Chan,C. A. Currat,M. P. Decowski,B. K. Fujikawa,R. Henning,K. T. Lesko,A. W. P. Poon,K. Tolich,J. Wang
Physics , 2006, DOI: 10.1007/s11038-006-9112-8
Abstract: A significant fraction of the 44TW of heat dissipation from the Earth's interior is believed to originate from the decays of terrestrial uranium and thorium. The only estimates of this radiogenic heat, which is the driving force for mantle convection, come from Earth models based on meteorites, and have large systematic errors. The detection of electron antineutrinos produced by these uranium and thorium decays would allow a more direct measure of the total uranium and thorium content, and hence radiogenic heat production in the Earth. We discuss the prospect of building an electron antineutrino detector approximately 700m^3 in size in the Homestake mine at the 4850' level. This would allow us to make a measurement of the total uranium and thorium content with a statistical error less than the systematic error from our current knowledge of neutrino oscillation parameters. It would also allow us to test the hypothesis of a naturally occurring nuclear reactor at the center of the Earth.
Search for a T-odd, P-even Triple Correlation in Neutron Decay
T. E. Chupp,R. L. Cooper,K. P. Coulter,S. J. Freedman,B. K. Fujikawa,A. García,G. L. Jones,H. P. Mumm,J. S. Nico,A. K. Thompson,C. A. Trull,F. E. Wietfeldt,J. F. Wilkerson
Statistics , 2012, DOI: 10.1103/PhysRevC.86.035505
Abstract: Background: Time-reversal-invariance violation, or equivalently CP violation, may explain the observed cosmological baryon asymmetry as well as signal physics beyond the Standard Model. In the decay of polarized neutrons, the triple correlation D\cdot(p_{e}\timesp_{\nu}) is a parity-even, time-reversal- odd observable that is uniquely sensitive to the relative phase of the axial-vector amplitude with respect to the vector amplitude. The triple correlation is also sensitive to possible contributions from scalar and tensor amplitudes. Final-state effects also contribute to D at the level of 1e-5 and can be calculated with a precision of 1% or better. Purpose: We have improved the sensitivity to T-odd, P-even interactions in nuclear beta decay. Methods: We measured proton-electron coincidences from decays of longitudinally polarized neutrons with a highly symmetric detector array designed to cancel the time-reversal-even, parity-odd Standard-Model contributions to polarized neutron decay. Over 300 million proton-electron coincidence events were used to extract D and study systematic effects in a blind analysis. Results: We find D = [-0.94\pm1.89(stat)\pm0.97(sys)]e-4. Conclusions: This is the most sensitive measurement of D in nuclear beta decay. Our result can be interpreted as a measurement of the phase of the ratio of the axial-vector and vector coupling constants (CA/CV= |{\lambda}|exp(i{\phi}_AV)) with {\phi}_AV = 180.012{\deg} \pm0.028{\deg} (68% confidence level) or to constrain time-reversal violating scalar and tensor interactions that arise in certain extensions to the Standard Model such as leptoquarks. This paper presents details of the experiment, analysis, and systematic- error corrections.
A New Limit on Time-Reversal Violation in Beta Decay
H. P. Mumm,T. E. Chupp,R. L. Cooper,K. P. Coulter,S. J. Freedman,B. K. Fujikawa,A. Garcia,G. L. Jones,J. S. Nico,A. K. Thompson,C. A. Trull,J. F. Wilkerson,F. E. Wietfeldt
Statistics , 2011, DOI: 10.1103/PhysRevLett.107.102301
Abstract: We report the results of an improved determination of the triple correlation $D P \cdot(p_{e}\times p_{\nu})$ that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the Standard Model. Our result is $D=(-0.96\pm 1.89 (stat)\pm 1.01 (sys))\times 10^{-4}$. The corresponding phase between g_A and g_V is $\phi_{AV} = 180.013^\circ\pm0.028^\circ$ (68 % confidence level). This result represents the most sensitive measurement of D in beta decay.
Constraints on left-right symmetric models from the process $b \rightarrow s γ$
K. S. Babu,Kazuo Fujikawa,Atsushi Yamada
Physics , 1993, DOI: 10.1016/0370-2693(94)91029-4
Abstract: In left-right symmetric models, large contributions to the decay amplitude $b \rightarrow s+ \gamma$ can arise from the mixing of the $W_L$ and $W_R$ gauge bosons as well as from the charged Higgs boson. These amplitudes are enhanced by the factor $\mt/\mb$ compared to the contributions in the standard model. We use the recent CLEO results on the radiative $B$ decay to place constraints on the $W_L-W_R$ mixing angle $\zeta$ and the mass of the charged Higgs boson $m_{H^\pm}$. Significant departures from the standard model predictions occur when $|\zeta| > 0.003$ and/or when $m_{H^\pm} < $ a few TeV.
Retro-mode imaging of fibrovascular membrane in proliferative diabetic retinopathy after intravitreal bevacizumab injection
Suzuma K, Tsuiki E, Matsumoto M, Fujikawa A, Kitaoka T
Clinical Ophthalmology , 2011, DOI: http://dx.doi.org/10.2147/OPTH.S22843
Abstract: ro-mode imaging of fibrovascular membrane in proliferative diabetic retinopathy after intravitreal bevacizumab injection Case report (2895) Total Article Views Authors: Suzuma K, Tsuiki E, Matsumoto M, Fujikawa A, Kitaoka T Published Date June 2011 Volume 2011:5 Pages 897 - 900 DOI: http://dx.doi.org/10.2147/OPTH.S22843 Kiyoshi Suzuma, Eiko Tsuiki, Makiko Matsumoto, Azusa Fujikawa, Takashi Kitaoka Department of Ophthalmology and Visual Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan Abstract: The F10 is a new commercially available scanning laser confocal ophthalmoscope (SLO) that can perform multiple functions. We determined the usefulness of noninvasive evaluation of proliferative diabetic retinopathy (PDR) pathologies before and after intravitreal injection of bevacizumab (IVB) using the new indirect viewing system of the retro-mode function of the F10 SLO, and compared the images histologically with surgically excised fibrovascular membrane from two cases. In PDR, neovascular vessels in fibrovascular membrane were clearly seen with the retro-mode, even after IVB and without blood flow. The F10 SLO may be useful in evaluating neovascular vessels in fibrovascular membrane in PDR and for determining the precise retinal changes in diabetic retinopathy.
Retro-mode imaging of fibrovascular membrane in proliferative diabetic retinopathy after intravitreal bevacizumab injection
Suzuma K,Tsuiki E,Matsumoto M,Fujikawa A
Clinical Ophthalmology , 2011,
Abstract: Kiyoshi Suzuma, Eiko Tsuiki, Makiko Matsumoto, Azusa Fujikawa, Takashi KitaokaDepartment of Ophthalmology and Visual Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, JapanAbstract: The F10 is a new commercially available scanning laser confocal ophthalmoscope (SLO) that can perform multiple functions. We determined the usefulness of noninvasive evaluation of proliferative diabetic retinopathy (PDR) pathologies before and after intravitreal injection of bevacizumab (IVB) using the new indirect viewing system of the retro-mode function of the F10 SLO, and compared the images histologically with surgically excised fibrovascular membrane from two cases. In PDR, neovascular vessels in fibrovascular membrane were clearly seen with the retro-mode, even after IVB and without blood flow. The F10 SLO may be useful in evaluating neovascular vessels in fibrovascular membrane in PDR and for determining the precise retinal changes in diabetic retinopathy.Keywords: bevacizumab, imaging, proliferative diabetic retinopathy, retro-mode, scanning laser ophthalmoscope
A New Measurement of the Partial 0+->0+ Half Life of 10C with GAMMASPHERE
B. K. Fujikawa,S. J. Asztalos,R. M. Clark,M. -A. Deleplanque-Stephens,P. Fallon,S. J. Freedman,I-Y. Lee,L. J. Lising,A. O. Macchiavelli,R. W. MacLeod,J. C. Reich,M. A. Rowe,S. -Q. Shang,F. S. Stephens,E. G. Wasserman,J. P. Greene
Physics , 1998,
Abstract: We report on a new measurement of the strength of the superallowed 0+->0+ transition in the beta-decay of 10C: 10C(0+,g.s.)->10B(0+,1.74MeV)+e+nu. The experiment was done at the LBNL 88-inch cyclotron using forty seven GAMMASPHERE germanium detectors. Precise knowledge of this branching ratio is necessary to compute the superallowed Fermi ft, which gives the weak vector coupling constant and the u to d element of the Cabibbo-Kobayashi- Maskawa quark mixing matrix.
Study of electron anti-neutrinos associated with gamma-ray bursts using KamLAND
K. Asakura,A. Gando,Y. Gando,T. Hachiya,S. Hayashida,H. Ikeda,K. Inoue,K. Ishidoshiro,T. Ishikawa,S. Ishio,M. Koga,S. Matsuda,T. Mitsui,D. Motoki,K. Nakamura,S. Obara,Y. Oki,T. Oura,I. Shimizu,Y. Shirahata,J. Shirai,A. Suzuki,H. Tachibana,K. Tamae,K. Ueshima,H. Watanabe,B. D. Xu,H. Yoshida,A. Kozlov,Y. Takemoto,S. Yoshida,K. Fushimi,A. Piepke,T. I. Banks,B. E. Berger,T. O'Donnell,B. K. Fujikawa,J. Maricic,J. G. Learned,M. Sakai,L. A. Winslow,Y. Efremenko,H. J. Karwowski,D. M. Markoff,W. Tornow,J. A. Detwiler,S. Enomoto,M. P. Decowski
Physics , 2015, DOI: 10.1088/0004-637X/806/1/87
Abstract: We search for electron anti-neutrinos ($\overline{\nu}_e$) 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 $\overline{\nu}_e$ fluence from GRBs below 7 MeV and place first constraints on the relation between $\overline{\nu}_e$ luminosity and effective temperature.
KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
K. Asakura,A. Gando,Y. Gando,T. Hachiya,S. Hayashida,H. Ikeda,K. Inoue,K. Ishidoshiro,T. Ishikawa,S. Ishio,M. Koga,S. Matsuda,T. Mitsui,D. Motoki,K. Nakamura,S. Obara,T. Oura,I. Shimizu,Y. Shirahata,J. Shirai,A. Suzuki,H. Tachibana,K. Tamae,K. Ueshima,H. Watanabe,B. D. Xu,A. Kozlov,Y. Takemoto,S. Yoshida,K. Fushimi,A. Piepke,T. I. Banks,B. E. Berger,B. K. Fujikawa,T. O'Donnell,J. G. Learned,J. Maricic,S. Matsuno,M. Sakai,L. A. Winslow,Y. Efremenko,H. J. Karwowski,D. M. Markoff,W. Tornow,J. A. Detwiler,S. Enomoto,M. P. Decowski
Physics , 2015,
Abstract: In the late stages of nuclear burning for massive stars ($M>8~M_{\sun}$), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of $25~M_{\sun}$ at a distance less than 660~pc with 3$\sigma$ significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.
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