Showing papers by "K. Nishikawa published in 1999"
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, Stony Brook University13, Niigata University14, Osaka University15, Seoul National University16, Tohoku University17, Tokai University18, Tokyo Institute of Technology19, University of Warsaw20, University of Washington21, California Institute of Technology22, Stanford University23
TL;DR: A total of 614 upward throughgoing muons were observed by Super-Kamiokande during 537 detector live days and the measured muon flux is [1.74{plus_minus} 0.02(sys)]{times} 10{sup {minus}13} cm{sup 2}thinsp2{theta} {gt}0.
Abstract: A total of 614 upward throughgoing muons of minimum energy 1.6thinspthinspGeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is [1.74{plus_minus}0.07(stat){plus_minus} 0.02(sys)]{times}10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} compared to an expected flux of [1.97{plus_minus}0.44(theor)]{times} 10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} . The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the {nu}{sub {mu}}{leftrightarrow}{nu}{sub {tau}} oscillation hypothesis with sin{sup 2}thinsp2{theta} {gt}0.4 and 1{times}10{sup {minus}3}{lt}{Delta}m{sup 2}{lt}1{times}1 0{sup {minus}1} eV{sup 2} at 90{percent} confidence level. {copyright} {ital 1999} {ital The American Physical Society}
429 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, Stanford University23
TL;DR: In this article, a search for day-night variations in the solar neutrino flux resulting from neutrinos oscillations has been carried out using the 504 day sample of solar NE data obtained at Super-Kamiokande.
Abstract: A search for day-night variations in the solar neutrino flux resulting from neutrino oscillations has been carried out using the 504 day sample of solar neutrino data obtained at Super-Kamiokande. The absence of a significant day-night variation has set an absolute flux independent exclusion region in the two neutrino oscillation parameter space.
287 citations
01 Jan 1999
TL;DR: A total of 614 upward through-going muons of minimum energy 1.6 GeV were observed by Super-Kamiokande during 537 detector live days as discussed by the authors.
Abstract: A total of 614 upward through-going muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is (1.74 ± 0.07(stat.) ± 0.02(sys.)) × 10 −13 cm −2 s −1 sr −1 compared to an expected flux of (1.97 ± 0.44(theo.)) × 10 −13 cm −2 s −1 sr −1 . The absolute measured flux is in agreement with the prediction within the errors. However, the zenith angle dependence of the observed upward through-going muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the �µ ↔ �� oscillation hypothesis with sin 2 2� > 0.4 and 1 × 10 −3 < �m 2 < 1 × 10 −1 eV 2 at 90 % confidence level.
285 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, California Institute of Technology23, Stanford University24
TL;DR: In this article, a measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super-Kamiokande detector is presented, where the shape of the measured spectrum is compared with the expectation for solar {sup 8}B neutrinos.
Abstract: A measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super-Kamiokande detector is presented. The results shown here were obtained from 504 days of data taken between 31 May 1996 and 25 March 1998. The shape of the measured spectrum is compared with the expectation for solar {sup 8}B neutrinos. The comparison takes into account both kinematic and detector related effects in the measurement process. The spectral shape comparison between the observation and the expectation gives a {chi}{sup 2} of 25.3 with 15 degrees of freedom, corresponding to a 4.6{percent} confidence level. {copyright} {ital 1999} {ital The American Physical Society}
253 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, George Mason University6, Gifu University7, Kobe University8, Kyoto University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, Stony Brook University13, Niigata University14, Osaka University15, Seoul National University16, Tohoku University17, Tokai University18, Tokyo Institute of Technology19, University of Warsaw20, California Institute of Technology21, University of Washington22
TL;DR: In this paper, the authors measured the upward through-going muon flux and calculated the stopping/through-going flux ratio R, which has less theoretical uncertainty than the expected values.
136 citations
Tokyo Institute of Technology1, Boston University2, University of Tokyo3, Brookhaven National Laboratory4, University of California, Irvine5, California State University6, George Mason University7, Gifu University8, University of Hawaii at Manoa9, Kobe University10, Los Alamos National Laboratory11, Louisiana State University12, University of Maryland, College Park13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, University of Warsaw20, California Institute of Technology21, University of Washington22, Stanford University23
TL;DR: In this article, the Super-Kamiokande detector was used to search for proton decays, and a lower bound on the partial lifetime of the proton was established.
Abstract: We present results of a search for proton decays, $p\ensuremath{\rightarrow}\overline{\ensuremath{
u}}{K}^{+}$, using data from a $33\mathrm{kt}\ifmmode \dot{}\else \.{}\fi{}\mathrm{yr}$ exposure of the Super-Kamiokande detector. Two decay modes of the kaon, ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{
u}}_{\ensuremath{\mu}}$ and ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$, were studied. The data were consistent with the background expected from atmospheric neutrinos; therefore a lower limit on the partial lifetime of the proton $\ensuremath{\tau}/B(p\ensuremath{\rightarrow}\overline{\ensuremath{
u}}{K}^{+})$ was found to be $6.7\ifmmode\times\else\texttimes\fi{}{10}^{32}\mathrm{years}$ at $90%$ confidence level.
93 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, George Mason University6, Gifu University7, University of Hawaii8, KEK9, Kobe University10, Los Alamos National Laboratory11, Louisiana State University12, University of Maryland, College Park13, State University of New York System14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22
21 Jan 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a linear accelerator (LINAC) for electrons was installed at the Super-Kamiokande experiment for solar neutrino measurements, and the absolute energy scale is now known with less than 1% uncertainty.
Abstract: In order to calibrate the Super-Kamiokande experiment for solar neutrino measurements, a linear accelerator (LINAC) for electrons was installed at the detector. LINAC data were taken at various positions in the detector volume, tracking the detector response in the variables relevant to solar neutrino analysis. In particular, the absolute energy scale is now known with less than 1% uncertainty.
81 citations
Tokyo Institute of Technology1, University of Tokyo2, Boston University3, Brookhaven National Laboratory4, University of California, Irvine5, California State University6, George Mason University7, Gifu University8, University of Hawaii at Manoa9, Kobe University10, Los Alamos National Laboratory11, Louisiana State University12, University of Maryland, College Park13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, University of Warsaw20, California Institute of Technology21, University of Washington22, Stanford University23
TL;DR: In this article, the east-west anisotropy caused by the deflection of primary cosmic rays in the Earth's magnetic field was observed for the first time in the flux of atmospheric neutrinos.
Abstract: The east-west anisotropy, caused by the deflection of primary cosmic rays in the Earth{close_quote}s magnetic field, is observed for the first time in the flux of atmospheric neutrinos. Using a 45thinspthinspktthinspyr exposure of the Super-Kamiokande detector, 552thinspthinspe -like and 633thinspthinsp{mu} -like horizontally going events are selected in the momentum range between 400 and 3000 thinspMeV/c . The azimuthal distributions of e -like and {mu} -like events agree with the expectation from atmospheric neutrino flux calculations, verifying that the flux of atmospheric neutrinos in the GeV energy range is reasonably well modeled by calculations that account for the geomagnetic field. {copyright} {ital 1999} {ital The American Physical Society}
74 citations
University of Tokyo1, Gifu University2, Tokai University3, Niigata University4, Boston University5, Brookhaven National Laboratory6, University of California, Irvine7, California State University, Dominguez Hills8, George Mason University9, University of Hawaii10, KEK11, Kobe University12, Los Alamos National Laboratory13, Louisiana State University14, University of Maryland, College Park15, State University of New York System16, Osaka University17, Seoul National University18, Tohoku University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22
TL;DR: In this paper, the measurement of radon concentrations at Super-Kamiokande, the method of Radon reduction, and the radon monitoring system were described. But the measurement showed that the current low-energy event rate between 5.0 MeV and 6.5 MeV implies a radon concentration in the Super Kamiokaande water of less than 1.4 mBq/m3.
36 citations