Showing papers by "Y. Hayato published in 2015"
TL;DR: In this article, the authors report on measurements of neutrino oscillation using data from the T2K long-baseline neutrinos experiment collected between 2010 and 2013 and find the following estimates and 68% confidence intervals for the two possible mass hierarchies: Normal Hierarchy:
Abstract: We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: Normal Hierarchy: $\sin^2\theta_{23}=0.514^{+0.055}_{-0.056}$ and $\Delta m^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ Inverted Hierarchy: $\sin^2\theta_{23}=0.511\pm0.055$ and $\Delta m^2_{13}=(2.48\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ The analysis accounts for multi-nucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region: $\delta_{CP}=[0.15,0.83]\pi$ for normal hierarchy and $\delta_{CP}=[-0.08,1.09]\pi$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes Factor of 2.2. The most probable values and 68% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: $\sin^2\theta_{23}=0.528^{+0.055}_{-0.038}$ and $|\Delta m^2_{32}|=(2.51\pm0.11)\times 10^{-3}$ eV$^2$/c$^4$.
302 citations
Nagoya University1, University of Tokyo2, Institute for the Physics and Mathematics of the Universe3, Boston University4, University of British Columbia5, Brookhaven National Laboratory6, University of California, Irvine7, California State University, Dominguez Hills8, Chonnam National University9, Duke University10, Fukuoka Institute of Technology11, Gifu University12, Gwangju Institute of Science and Technology13, University of Hawaii14, KEK15, Kobe University16, Kyoto University17, Miyagi University of Education18, Stony Brook University19, Okayama University20, Osaka University21, University of Regina22, TRIUMF23, Seoul National University24, Shizuoka University25, Sungkyunkwan University26, Tokai University27, University of Toronto28, Tsinghua University29, University of Washington30
TL;DR: In this article, the authors considered neutrino events with interaction vertices in the SK detector in addition to upward-going muons produced in the surrounding rock and found no significant excess over expected atmospheric-neutrino background and interpreted the result in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel.
Abstract: Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bb[over ¯] and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.
297 citations
TL;DR: In this paper, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and neutrinos from the J-PARC proton synchrotron is presented.
Abstract: Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of $CP$ asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams.
In this paper, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5 MW $\times$ 10$^7$ sec integrated proton beam power (corresponding to $1.56\times10^{22}$ protons on target with a 30 GeV proton beam) to a $2.5$-degree off-axis neutrino beam, it is expected that the leptonic $CP$ phase $\delta_{CP}$ can be determined to better than 19 degrees for all possible values of $\delta_{CP}$, and $CP$ violation can be established with a statistical significance of more than $3\,\sigma$ ($5\,\sigma$) for $76\%$ ($58\%$) of the $\delta_{CP}$ parameter space. Using both $
u_e$ appearance and $
u_\mu$ disappearance data, the expected 1$\sigma$ uncertainty of $\sin^2\theta_{23}$ is 0.015(0.006) for $\sin^2\theta_{23}=0.5(0.45)$.
174 citations
University of Tokyo1, Autonomous University of Madrid2, Boston University3, University of British Columbia4, Brookhaven National Laboratory5, University of California, Irvine6, California State University, Dominguez Hills7, Chonnam National University8, Duke University9, Fukuoka Institute of Technology10, Gifu University11, Gwangju Institute of Science and Technology12, Kobe University13, Kyoto University14, Miyagi University of Education15, Nagoya University16, Stony Brook University17, Okayama University18, Osaka University19, TRIUMF20, University of Regina21, Seoul National University22, Shizuoka University23, Sungkyunkwan University24, Tokai University25, University of Toronto26, Tsinghua University27, University of Washington28
TL;DR: Using atmospheric neutrino data from the Super-Kamiokande experiment, the authors of as mentioned in this paper found new limits on the sterile neutrinos oscillations, showing that there should exist at least one more type of neutrines in nature.
Abstract: Are there more than three types of neutrinos in nature ? Some experiments show that there should exist at least one more type, called sterile neutrinos. Using atmospheric neutrino data from the Super-Kamiokande experiment, the authors find new limits on the sterile neutrino oscillations.
160 citations
Tsinghua University1, University of Tokyo2, University of British Columbia3, Boston University4, Brookhaven National Laboratory5, University of California, Irvine6, California State University, Dominguez Hills7, Chonnam National University8, Duke University9, Fukuoka Institute of Technology10, Gifu University11, University of Hawaii12, KEK13, Kobe University14, Kyoto University15, Miyagi University of Education16, Nagoya University17, Stony Brook University18, Okayama University19, Osaka University20, University of Regina21, Seoul National University22, Shizuoka University23, Sungkyunkwan University24, Tokai University25, Institute for the Physics and Mathematics of the Universe26, TRIUMF27, University of Washington28
TL;DR: In this paper, a search for Supernova Relic Neutrinos ν ¯ e ’s was conducted via inverse-beta-decay by tagging neutron capture on hydrogen at Super-Kamiokande-IV.
109 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, Chonnam National University6, Duke University7, George Mason University8, Gifu University9, Indiana University10, Kobe University11, Kyoto University12, Los Alamos National Laboratory13, Louisiana State University14, University of Maryland, College Park15, University of Minnesota16, Miyagi University of Education17, Nagoya University18, Stony Brook University19, Niigata University20, Okayama University21, Osaka University22, Seoul National University23, Shizuoka University24, Sungkyunkwan University25, Tohoku University26, Tokai University27, Tokyo Institute of Technology28, Tsinghua University29, University of Warsaw30, University of Washington31
TL;DR: A search for neutrino-antineutron (n-n¯) oscillation was undertaken in Super-Kamiokande using the 1489 live-day or 2.45×1034 neutron-year exposure data.
Abstract: Author(s): Abe, K; Hayato, Y; Iida, T; Ishihara, K; Kameda, J; Koshio, Y; Minamino, A; Mitsuda, C; Miura, M; Moriyama, S; Nakahata, M; Obayashi, Y; Ogawa, H; Sekiya, H; Shiozawa, M; Suzuki, Y; Takeda, A; Takeuchi, Y; Ueshima, K; Watanabe, H; Higuchi, I; Ishihara, C; Ishitsuka, M; Kajita, T; Kaneyuki, K; Mitsuka, G; Nakayama, S; Nishino, H; Okumura, K; Saji, C; Takenaga, Y; Clark, S; Desai, S; Dufour, F; Herfurth, A; Kearns, E; Likhoded, S; Litos, M; Raaf, JL; Stone, JL; Sulak, LR; Wang, W; Goldhaber, M; Casper, D; Cravens, JP; Dunmore, J; Griskevich, J; Kropp, WR; Liu, DW; Mine, S; Regis, C; Smy, MB; Sobel, HW; Vagins, MR; Ganezer, KS; Hartfiel, B; Hill, J; Keig, WE; Jang, JS; Jeoung, IS; Kim, JY; Lim, IT; Scholberg, K; Tanimoto, N; Walter, CW; Wendell, R; Ellsworth, RW; Tasaka, S; Guillian, G; Learned, JG; Matsuno, S; Messier, MD; Ichikawa, AK; Ishida, T; Ishii, T; Iwashita, T; Kobayashi, T; Nakadaira, T; Nakamura, K; Nishikawa, K; Nitta, K; Oyama, Y; Suzuki, AT; Hasegawa, M; Maesaka, H | Abstract: A search for neutron-antineutron (n-n¯) oscillation was undertaken in Super-Kamiokande using the 1489 live-day or 2.45×1034 neutron-year exposure data. This process violates both baryon and baryon minus lepton numbers by an absolute value of two units and is predicted by a large class of hypothetical models where the seesaw mechanism is incorporated to explain the observed tiny neutrino masses and the matter-antimatter asymmetry in the Universe. No evidence for n-n¯ oscillation was found; the lower limit of the lifetime for neutrons bound in O16, in an analysis that included all of the significant sources of experimental uncertainties, was determined to be 1.9×1032years at the 90% confidence level. The corresponding lower limit for the oscillation time of free neutrons was calculated to be 2.7×108s using a theoretical value of the nuclear suppression factor of 0.517×1023s-1 and its uncertainty.
103 citations
University of Tokyo1, Autonomous University of Madrid2, Boston University3, University of British Columbia4, Brookhaven National Laboratory5, University of California, Irvine6, California State University, Dominguez Hills7, Chonnam National University8, Duke University9, Fukuoka Institute of Technology10, Gifu University11, Gwangju Institute of Science and Technology12, Kobe University13, Kyoto University14, Miyagi University of Education15, Nagoya University16, Stony Brook University17, Okayama University18, Osaka University19, TRIUMF20, University of Regina21, Seoul National University22, Shizuoka University23, Sungkyunkwan University24, Tokai University25, University of Toronto26, Tsinghua University27, University of Washington28
TL;DR: In this article, a search for neutrino oscillations induced by Lorentz violation was performed using 4,438 live-days of Super-Kamiokande atmospheric neutrinos data.
Abstract: A search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data The Lorentz violation is included in addition to standard three-flavor oscillations using the nonperturbative standard model extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the e μ , μ τ , and e τ sectors, improving the existing limits by up to 7 orders of magnitude and setting limits for the first time in the neutrino μ τ sector of the SME
82 citations
TL;DR: In this article, the authors acknowledge the support of MEXT, Japan; NSERC, NRC, and======CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; MICINN and CPAN, Spain; SNSF and SER, Switzerland; STFC, UK; and DOE, USA.
Abstract: We thank the J-PARC staff for superb accelerator performance and the CERN NA61 collaboration for providing
valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC, and
CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN),
Poland; RAS, RFBR, and MES, Russia; MICINN and CPAN, Spain; SNSF and SER, Switzerland; STFC, UK;
and DOE, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover
system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK. In addition,
participation of individual researchers and institutions has been further supported by funds from: ERC (FP7),
EU; JSPS, Japan; Royal Society, UK; DOE Early Career program, USA.
73 citations
Posted Content•
Nagoya University1, University of Tokyo2, University of British Columbia3, Brookhaven National Laboratory4, University of California, Irvine5, California State University, Dominguez Hills6, Chonnam National University7, Duke University8, Fukuoka Institute of Technology9, Gifu University10, Gwangju Institute of Science and Technology11, University of Hawaii12, Kobe University13, Kyoto University14, Miyagi University of Education15, Stony Brook University16, Okayama University17, Osaka University18, Seoul National University19, Shizuoka University20, Sungkyunkwan University21, Tokai University22, Institute for the Physics and Mathematics of the Universe23, University of Toronto24, TRIUMF25, Tsinghua University26, University of Washington27
TL;DR: This analysis includes neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock, finding no significant excess over expected atmospheric-neutrino background and upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel.
Abstract: Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/$c^2$ $\sim$ 200-GeV/$c^2$) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent (SD) WIMP-proton cross section for WIMP masses below 200 GeV/$c^2$ (at 10 GeV/$c^2$, 1.49$\times 10^{-39}$ cm$^2$ for $\chi\chi\rightarrow b \bar{b}$ and 1.31$\times 10^{-40}$ cm$^2$ for $\chi\chi\rightarrow\tau^+\tau^-$ annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent (SI) coupling in the few-GeV/$c^2$ mass range.
66 citations
TL;DR: In this article, the authors acknowledge the support of MEXT, Japan, NSERC, NRC, and CFI, Canada, CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR, and MES, Russia; MINECO and ERDF funds, Morocco; SNSF and SER, Switzerland; STFC, UK; and DOE, USA.
Abstract: We thank the J-PARC staff for superb accelerator
performance and the CERN NA61 Collaboration for
providing valuable particle production data. We acknowledge
the support of MEXT, Japan; NSERC, NRC, and CFI,
Canada; CEA and CNRS/IN2P3, France; DFG, Germany;
INFN, Italy; National Science Centre (NCN), Poland; RSF,
RFBR, and MES, Russia; MINECO and ERDF funds,
Spain; SNSF and SER, Switzerland; STFC, UK; and DOE,
USA. We also thank CERN for the UA1/NOMAD magnet,
DESY for the HERA-B magnet mover system, NII for
SINET4, the WestGrid and SciNet consortia in Compute
Canada, GridPP, UK. In addition participation of individual
researchers and institutions has been further supported by
funds from ERC (FP7), EU; JSPS, Japan; Royal Society,
UK; DOE Early Career program, USA.
52 citations
TL;DR: In this paper, a measurement of the charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam at mean neutrinos energies of 1.94 GeV and 0.93 GeV are reported.
Abstract: We report a measurement of the $
u_\mu$ charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasi-elastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are $(11.95\pm 0.19(stat.)_{-1.47}^{+1.82} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$ and $(10.64\pm 0.37(stat.)_{-1.65}^{+2.03} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.
TL;DR: Search results for nucleon decays p→e^{+}X, p→μ^{+]X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decay np→e−ν, np→μ+}ν, and np→τ−ν in the Super-Kamiokande experiment are presented.
Abstract: Search results for nucleon decays p→e^{+}X, p→μ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→μ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→μ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32} yr, τ_{np→μ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.
TL;DR: The T2K experiment has performed a search for ''nu_e$ disappearance due to sterile neutrinos using $5.9 \times 10^{20}$ protons on target for a baseline of $280 m$ in a neutrino beam peaked at about $500 MeV'' as discussed by the authors.
Abstract: The T2K experiment has performed a search for $
u_e$ disappearance due to sterile neutrinos using $5.9 \times 10^{20}$ protons on target for a baseline of $280 m$ in a neutrino beam peaked at about $500 MeV$. A sample of
u_e CC interactions in the off-axis near detector has been selected with a purity of 63\% and an efficiency of 26\%. The p-value for the null hypothesis is 0.085 and the excluded region at 95\% CL is approximately $sin^2 2 \theta_{ee} > 0.3$ for $\Delta m^2_{eff} > 7 eV^2 / c^4$.
TL;DR: In this paper, a microscopic model for single photon emission in neutral current interactions on nucleons and nuclei was applied to determine the number and distributions of such events at the Super-Kamiokande detector, for the flux and beam exposure of the T2K experiment in neutrino mode.
Abstract: We have applied a microscopic model for single photon emission in neutral current interactions on nucleons and nuclei to determine the number and distributions of such events at the Super-Kamiokande detector, for the flux and beam exposure of the T2K experiment in neutrino mode. These reactions represent an irreducible background in electron-(anti)neutrino appearance measurements aimed at a precise measurement of mixing angle $\theta_{13}$ and the $CP$ violating phase. We have obtained a total number of photon events that is twice larger than the one from the NEUT event generator (version 5.1.4.2) used in the analysis of T2K data. Detailed comparisons of energy and angular distributions for the $
u_\mu$ and $\bar
u_\mu$ fluxes have also been performed.
TL;DR: In this article, the JPARC staff and the CERN NA61 collaboration provided valuable particle production data and the support of MEXT, Japan; NSERC, NRC and CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR and MES, Russia; MINECO and ERDF funds,======Spain; SNSF and SER, Switzerland; STFC, U.K.; and======DOE,
Abstract: We thank the J-PARC staff for superb accelerator
performance and the CERN NA61 collaboration for providing
valuable particle production data. We acknowledge
the support of MEXT, Japan; NSERC, NRC and CFI,
Canada; CEA and CNRS/IN2P3, France; DFG, Germany;
INFN, Italy; National Science Centre (NCN), Poland; RSF,
RFBR and MES, Russia; MINECO and ERDF funds,
Spain; SNSF and SER, Switzerland; STFC, U.K.; and
DOE, U.S.A. We also thank CERN for the UA1/NOMAD
magnet, DESY for the HERA-B magnet mover system, NII
for SINET4, the WestGrid and SciNet consortia in
Compute Canada, GridPP, U.K. In addition participation
of individual researchers and institutions has been further
supported by funds from: ERC (FP7), EU; JSPS, Japan;
Royal Society, U.K.; DOE Early Career program, U.S.A.
15 May 2015
TL;DR: In this article, the neutrino-nucleus interaction in each region has quite different characteristics, from the quasi-elastic, through the resonance region, to the deeply inelastic scattering region.
Abstract: Next generation neutrino oscillation experiments will need a quantitative understanding of neutrino-nucleus interaction far better than ever. Kinematics covered by the relevant neutrino-nucleus interaction spans wide region, from the quasi-elastic, through the resonance region, to the deeply inelastic scattering region. The neutrino-nucleus interaction in each region has quite different characteristics. Obviously, it is essential to combine different expertise to construct a unified model that covers all the kinematical region of the neutrino-nucleus interaction. Recently, several experimentalists and theorists got together to form a collaboration to tackle this problem. In this contribution, we report the collaboration’s recent activity and a goal in near future.