Showing papers by "K. Nishikawa published in 2012"
University of California, Irvine1, University of Tokyo2, Autonomous University of Madrid3, Boston University4, California State University, Dominguez Hills5, Chonnam National University6, Duke University7, Fukuoka Institute of Technology8, Gifu University9, Kobe University10, Kyoto University11, Miyagi University of Education12, Nagoya University13, Stony Brook University14, Okayama University15, Osaka University16, Seoul National University17, Shizuoka University18, Sungkyunkwan University19, Tokai University20, Tsinghua University21, University of Warsaw22, University of Washington23
TL;DR: A new Super-Kamiokande search for supernova relic neutrinos was conducted using 2853 live days of data as mentioned in this paper, and the results showed that the neutrino flux was between 2.8 and 3.3 MeV.
Abstract: A new Super-Kamiokande search for supernova relic neutrinos was conducted using 2853 live days of data. Sensitivity is now greatly improved compared to the 2003 Super-Kamiokande result, which placed a flux limit near many theoretical predictions. This more detailed analysis includes a variety of improvements such as increased efficiency, a lower energy threshold, and an expanded data set. New combined upper limits on supernova relic neutrino flux are between 2.8 and $3.1{\overline{\ensuremath{
u}}}_{e}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}g16\text{ }\text{ }\mathrm{MeV}$ total positron energy (17.3 MeV ${\mathrm{E}}_{\ensuremath{
u}}$).
203 citations
TL;DR: In this article, the authors reported a measurement of muon-neutrino disappearance in the T2K experiment, which is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment.
Abstract: We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to 1.43 x 10(20) protons on target, we observe 31 fully-contained single mu-like ring events in Super-Kamiokande, compared with an expectation of 104 +/- 14 (syst) events without neutrino oscillations. The best-fit point for two-flavor nu(mu) -> nu(tau) oscillations is sin(2)(2 theta(23)) = 0.98 and vertical bar Delta m(32)(2)vertical bar = 2.65 x 10(-3) eV(2). The boundary of the 90% confidence region includes the points sin(2)(2 theta(23)), vertical bar Delta m(32)(2)vertical bar = (1.0, 3.1 x 10(-3) eV(2)), (0.84, 2.65 x 10(-3) eV(2)) and (1.0, 2.2 x 10(-3) eV(2)).
112 citations
01 Dec 2012-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Interactive Neutrino GRID (INGRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment.
Abstract: Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision.
104 citations
University of Geneva1, University of Warsaw2, National and Kapodistrian University of Athens3, Joint Institute for Nuclear Research4, Karlsruhe Institute of Technology5, Warsaw University of Technology6, Hungarian Academy of Sciences7, Federico Santa María Technical University8, Jagiellonian University9, University of Silesia in Katowice10, Pusan National University11, ETH Zurich12, Pierre-and-Marie-Curie University13, University of Bern14, Saint Petersburg State University15, Eötvös Loránd University16, Goethe University Frankfurt17, Jan Kochanowski University18, University of Wrocław19, Stony Brook University20, Frankfurt University of Applied Sciences21, University of Bergen22
TL;DR: In this paper, a graphite target with a thickness of 4% of a nuclear interaction length was used to measure positively charged kaons in p+C interactions at 31 GeV/c.
Abstract: Spectra of positively charged kaons in p+C interactions at 31 GeV/c were measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2007 with a graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections and charged pion spectra were already measured using the same set of data. These new measurements in combination with the published ones are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. In particular, the knowledge of kaon production is crucial for precisely predicting the intrinsic electron neutrino component and the high energy tail of the T2K beam. The results are presented as a function of laboratory momentum in 2 intervals of the laboratory polar angle covering the range from 20 up to 240 mrad. The kaon spectra are compared with predictions of several hadron production models. Using the published pion results and the new kaon data, the K+/\pi+ ratios are computed.
98 citations
University of Tokyo1, University of California, Berkeley2, Boston University3, Brookhaven National Laboratory4, University of California, Irvine5, California State University, Dominguez Hills6, Chonnam National University7, Duke University8, Fukuoka Institute of Technology9, Gifu University10, Kanagawa University11, Kobe University12, Kyoto University13, Miyagi University of Education14, Nagoya University15, Stony Brook University16, Niigata University17, Okayama University18, Osaka University19, Seoul National University20, Shizuoka University21, Sungkyunkwan University22, Tokai University23, Tsinghua University24, University of Warsaw25, University of Washington26
TL;DR: In this paper, lower limits on the nucleon partial lifetime at 90% confidence level were obtained, ranging from $3.6 to $8.2, depending on the decay modes.
Abstract: Searches for a nucleon decay into a charged antilepton (${e}^{+}$ or ${\ensuremath{\mu}}^{+}$) plus a light meson (${\ensuremath{\pi}}^{0}$, ${\ensuremath{\pi}}^{\ensuremath{-}}$, $\ensuremath{\eta}$, ${\ensuremath{\rho}}^{0}$, ${\ensuremath{\rho}}^{\ensuremath{-}}$, $\ensuremath{\omega}$) were performed using the Super-Kamiokande I and II data. Twelve nucleon decay modes were searched for. The total exposure is $140.9\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{years}$, which includes a $91.7\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ exposure (1489.2 live days) of Super-Kamiokande-I and a $49.2\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ exposure (798.6 live days) of Super-Kamiokande II. The number of candidate events in the data was consistent with the atmospheric neutrino background expectation. No significant evidence for a nucleon decay was observed in the data. Thus, lower limits on the nucleon partial lifetime at 90% confidence level were obtained. The limits range from $3.6\ifmmode\times\else\texttimes\fi{}{10}^{31}$ to $8.2\ifmmode\times\else\texttimes\fi{}{10}^{33}\text{ }\text{ }\mathrm{years}$, depending on the decay modes.
76 citations
University of California, Irvine1, University of Tokyo2, Autonomous University of Madrid3, Boston University4, Brookhaven National Laboratory5, California State University, Dominguez Hills6, Gwangju Institute of Science and Technology7, Chonnam National University8, Duke University9, Fukuoka Institute of Technology10, Gifu University11, Kobe University12, Kyoto University13, Miyagi University of Education14, Nagoya University15, Stony Brook University16, Okayama University17, Osaka University18, Seoul National University19, Shizuoka University20, Sungkyunkwan University21, Tokai University22, Tsinghua University23, University of Washington24
TL;DR: In this article, a lower bound of $1.6 was established for the probability of proton decay in this mode at the 90% confidence level, and the number of candidate events in the data was consistent with the atmospheric neutrino background expectation.
Abstract: We have searched for proton decay via $p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{K}^{0}$ using data from a $91.7\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ exposure of Super-Kamiokande- I, a $49.2\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ exposure of Super-Kamiokande II, and a $31.9\text{ }\text{ }\mathrm{kiloton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ exposure of Super-Kamiokande III. The number of candidate events in the data was consistent with the atmospheric neutrino background expectation and no evidence for proton decay in this mode was found. We set a partial lifetime lower limit of $1.6\ifmmode\times\else\texttimes\fi{}{10}^{33}\text{ }\text{ }\mathrm{years}$ at the 90% confidence level.
40 citations
University of Tokyo1, Institute for the Physics and Mathematics of the Universe2, Boston University3, University of California, Irvine4, California State University, Dominguez Hills5, Chonnam National University6, Duke University7, Fukuoka Institute of Technology8, Gifu University9, University of Hawaii10, KEK11, Kobe University12, Kyoto University13, Miyagi University of Education14, Nagoya University15, State University of New York System16, Okayama University17, Osaka University18, Seoul National University19, Shizuoka University20, Sungkyunkwan University21, Tokai University22, Tsinghua University23, University of Warsaw24, University of Washington25
TL;DR: In this article, a search for low energy neutrinos in the electron total energy range from 19 to 55 MeV was carried out with SK and gave a monopole flux limit of F M ( σ 0 / 1 mb ) 6.3 × 10 - 24 ( β M / 10 - 3 ) 2 cm - 2 s - 1 sr - 1 at 90% C.L.
35 citations
TL;DR: In this paper, the authors search for proton decay in muon plus neutral kaon using data from a 917 kiloton-year exposure of Super-Kamiokande-I, a 492 kiloton year exposure of Kamiokende-II, and a 319 kiloton years exposure of SKI-III and set a partial lifetime lower limit of 16x10^33 years at the 90% confidence level.
Abstract: We have searched for proton into muon plus neutral kaon using data from a 917 kiloton-year exposure of Super-Kamiokande-I, a 492 kiloton-year exposure of Super-Kamiokande-II, and a 319 kiloton-year exposure of Super-Kamiokande-III The number of candidate events in the data was consistent with the atmospheric neutrino background expectation and no evidence for proton decay in this mode was found We set a partial lifetime lower limit of 16x10^33 years at the 90% confidence level
16 citations
25 Jun 2012
TL;DR: Within the three-flavor mixing framework, there are three mixing angles (!!",!!",!!"), two independent mass splittings characterized by Δ!!"! and Δ!"!.
Abstract: Neutrino oscillations have been firmly established by experiments that measure solar neutrinos, atmospheric neutrinos, reactor antineutrinos, and accelerator-produced neutrinos and antineutrinos. To a first approximation, three-flavor mixing provides a good description of the neutrino oscillation phenomenology. Within the three-flavor mixing framework there are three mixing angles (!!", !!", !!"), two independent mass splittings characterized by Δ!!" ! and Δ!!" !
3 citations
Posted Content•
TL;DR: In this article, a liquid Argon TPC detector with fiducial mass of 150 kg was constructed as part of the R&D program of the next generation neutrino and nucleon decay detector.
Abstract: We have constructed a liquid Argon TPC detector with fiducial mass of 150 kg as a part of the R&D program of the next generation neutrino and nucleon decay detector. This paper describes a study of particle identification performance of the detector using well-defined charged particles (pions, kaons, and protons) with momentum of ~800 MeV/$c$ obtained at J-PARC K1.1BR beamline.
1 citations