T. Hasegawa
A5065356713- Particle physics theoretical and experimental studies
- Neutrino Physics Research
- Astrophysics and Cosmic Phenomena
- Quantum Chromodynamics and Particle Interactions
- Dark Matter and Cosmic Phenomena
- High-Energy Particle Collisions Research
- Physics of Superconductivity and Magnetism
- Nuclear Physics and Applications
- Nuclear physics research studies
- Particle Detector Development and Performance
- Atomic and Subatomic Physics Research
- Radiation Detection and Scintillator Technologies
- Advanced NMR Techniques and Applications
- Particle accelerators and beam dynamics
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Semiconductor Quantum Structures and Devices
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Muon and positron interactions and applications
- Rare-earth and actinide compounds
- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Iron-based superconductors research
- X-ray Spectroscopy and Fluorescence Analysis
High Energy Accelerator Research Organization
2016-2025
The University of Tokyo
2012-2024
Nagoya University
1998-2024
Kavli Institute for the Physics and Mathematics of the Universe
2016-2024
Institute for Cosmic Ray Research
2024
Obayashi (Japan)
2024
University of Toyama
2005-2024
Fukuoka Institute of Technology Junior College
2024
Osaka Institute of Technology
2020-2024
University of Bern
2023
We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure the Super-Kamiokande detector. The exhibit zenith angle dependent deficit muon neutrinos which is inconsistent with expectations based on calculations flux. Experimental biases and uncertainties in prediction fluxes cross sections are unable to explain our observation. consistent, however, two-flavor...
Solar neutrino measurements from 1258 days of data the Super-Kamiokande detector are presented. The based on recoil electrons in energy range 5.0--20.0 MeV. measured solar flux is $2.32\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{stat}{)}_{\ensuremath{-}0.07}^{+0.08}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{6}{\mathrm{cm}}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}$, which $45.1\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{stat}{)}_{\ensuremath{-}1.4}^{+1.6}(\mathrm{syst})%$ that...
The K2K experiment observes indications of neutrino oscillation: a reduction $\nu_\mu$ flux together with distortion the energy spectrum. Fifty-six beam events are observed in Super-Kamiokande (SK), 250 km from production point, an expectation $80.1^{+6.2}_{-5.4}$. Twenty-nine one ring $\mu$-like used to reconstruct spectrum, which is better matched expected spectrum oscillation than without. probability that at SK explained by statistical fluctuation without less 1%.
We present measurements of nu_mu disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One hundred and twelve beam-originated events are observed fiducial volume Super-Kamiokande with an expectation 158.1^{+9.2}_{-8.6} without oscillation. A distortion energy spectrum is also seen 58 single-ring muon-like reconstructed energies. The probability that observations explained by for no 0.0015% (4.3sigma). In a two flavor scenario, allowed Delta m^2 region at...
The previously published atmospheric neutrino data did not distinguish whether muon neutrinos were oscillating into tau or sterile neutrinos, as both hypotheses fit the data. Using recorded in 1100 live days of Super-Kamiokande detector, we use three complementary samples to study difference zenith angle distribution due neutral currents and matter effects. We find no evidence favoring reject hypothesis at 99% confidence level. On other hand, that oscillation between suffices explain all...
We report the result of a search for neutrino oscillations using precise measurements recoil electron energy spectrum and zenith angle variations solar flux from 1258 days neutrino-electron scattering data in Super-Kamiokande. The absence significant variation distortion places strong constraints on mixing mass difference flux-independent way. Using Super-Kamiokande measurement addition, two allowed regions at large are found.Received 19 March...
A total of 614 upward throughgoing muons 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)]×10−13cm−2s−1sr−1 compared to an expected [1.97±0.44(theor)]×10−13cm−2s−1sr−1. absolute in agreement with the prediction within errors. However, zenith-angle dependence does not agree no-oscillation predictions. distortion shape consistent νμ↔ντ oscillation hypothesis sin22θ>0.4 and 1×10−3<Δm2<1×10−1eV2 at 90%...
The T2K experiment has observed electron neutrino appearance in a muon beam produced 295 km from the Super-Kamiokande detector with peak energy of 0.6 GeV. A total 28 events were detected an distribution consistent signal, corresponding to significance 7.3σ when compared 4.92±0.55 expected background events. In Pontecorvo-Maki-Nakagawa-Sakata mixing model, signal depends on several parameters including three angles θ12, θ23, θ13, mass difference Δm232 and CP violating phase δCP. this...
We present results for ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ oscillation in the KEK to Kamioka (K2K) long-baseline neutrino experiment. K2K uses an accelerator-produced beam with a mean energy of 1.3 GeV directed at Super-Kamiokande detector. observed energy-dependent disappearance ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, which we presume have oscillated ${\ensuremath{\nu}}_{\ensuremath{\tau}}$. The probability that would observe these if there is no 0.0050% ($4.0\ensuremath{\sigma}$).
The flavor ratio of the atmospheric neutrino flux and its zenith angle dependence have been studied in multi-GeV energy range using an exposure 25.5 kiloton-years Super-Kamiokande detector. By comparing data to a detailed Monte Carlo simulation, (μ/e)DATA/(μ/e)MC was measured be 0.66±0.06(stat.)±0.08(sys.). In addition, strong distortion shape μ-like event distribution observed. number upward downward events found 0.52+0.07−0.06(stat.)±0.01(sys.), with expected value...
The results of the third phase Super-Kamiokande solar neutrino measurement are presented and compared to first second results. With improved detector calibrations, a full simulation, analysis methods, systematic uncertainty on total flux is estimated be ?2.1%, which about two thirds for Super-Kamiokande. observed 8B in 5.0 20 MeV electron energy region 2.32+/-0.04 (stat.)+/-0.05 (sys.) *10^6 cm^-2sec^-1, agreement with previous measurements. A combined oscillation carried out using SK-I, II,...
Precise measurements of the spin structure functions proton ${g}_{1}^{p}(x,{Q}^{2})$ and deuteron ${g}_{1}^{d}(x,{Q}^{2})$ are presented over kinematic range $0.0041\ensuremath{\le}x\ensuremath{\le}0.9$ $0.18\text{ }\text{ }{\mathrm{GeV}}^{2}\ensuremath{\le}{Q}^{2}\ensuremath{\le}20\text{ }{\mathrm{GeV}}^{2}$. The data were collected at HERMES experiment DESY, in deep-inelastic scattering 27.6 GeV longitudinally polarized positrons off hydrogen deuterium gas targets internal to HERA storage...
We present a search for non-zero theta_{13} and deviations of sin^2 theta_{23} from 0.5 in the oscillations atmospheric neutrino data Super-Kamiokande -I, -II, -III. No distortions flux consistent with are found both mass hierarchy hypotheses agreement data. The best fit at Delta m^2 = 2.1 x 10^-3 eV^2, 0.0, =0.5. In normal (inverted) constrained one-dimensional 90% C.L. to < 0.04 (0.09) 1.9 (1.7) 2.6 (2.7) eV^2. mixing angle is within 0.407 <= 0.583
We report on measurements of neutrino oscillation using data from the T2K long-baseline experiment collected between 2010 and 2013. In an analysis muon disappearance alone, we find following estimates 68% confidence intervals for two possible mass hierarchies: Normal Hierarchy: $\sin^2\theta_{23}=0.514^{+0.055}_{-0.056}$ $\Delta m^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ Inverted $\sin^2\theta_{23}=0.511\pm0.055$ m^2_{13}=(2.48\pm0.10)\times The accounts multi-nucleon mechanisms in...
After important upgrades to the experiment, Super-Kamiokande collaboration returns measuring solar mixing angle and mass splitting $\mathrm{\ensuremath{\Delta}}\phantom{\rule{0}{0ex}}{m}_{12}^{2}$. By focusing on low-energy ${}^{8}B$ neutrinos, is able single out neutrinos that undergo flavor conversion only through vacuum oscillations. The results are currently most precise values for mass-difference parameters relevant neutrino
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 detector addition to upward-going muons surrounding rock. Compared previous result, which used only, signal acceptances light (few−GeV/c2−200−GeV/c2) WIMPs are significantly increased. We fit 3903 days of SK data contribution annihilation found no...
An analysis of atmospheric neutrino data from all four run periods \superk optimized for sensitivity to the mass hierarchy is presented. Confidence intervals $\Delta m^2_{32}$, $\sin^2 \theta_{23}$, \theta_{13}$ and $\delta_{CP}$ are presented normal inverted hypotheses based on alone. Additional constraints reactor $\theta_{13}$ published binned T2K muon disappearance electron appearance added fit give enhanced above parameters. Over range parameters allowed at 90% confidence level, favored...
The Tokai-to-Kamioka (T2K) experiment studies neutrino oscillations using an off-axis muon beam with a peak energy of about 0.6 GeV that originates at the J-PARC accelerator facility. Interactions neutrinos are observed near detectors placed 280 m from production target and far detector -- Super-Kamiokande (SK) located 295 km away. flux prediction is essential part successful interaction rates T2K important input to oscillation cross section measurements. A FLUKA GEANT3 based simulation...
The T2K experiment measures muon neutrino disappearance and electron appearance in accelerator-produced antineutrino beams. With an exposure of 14.7(7.6)×1020 protons on target the (antineutrino) mode, 89 νe candidates seven anti-νe are observed, while 67.5 9.0 expected for δCP=0 normal mass ordering. obtained 2σ confidence interval CP-violating phase, δCP, does not include CP-conserving cases (δCP=0, π). best-fit values other parameters sin2θ23=0.526+0.032−0.036 Δm232=2.463+0.071−0.070×10−3...
New data from the T2K neutrino oscillation experiment produce most precise measurement of mixing parameter ${\ensuremath{\theta}}_{23}$. Using an off-axis beam with a peak energy 0.6 GeV and set corresponding to $6.57\ifmmode\times\else\texttimes\fi{}1{0}^{20}$ protons on target, has fit energy-dependent ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ probability determine parameters. The 68% confidence limit ${\mathrm{sin}}^{2}({\ensuremath{\theta}}_{23})$ is...
We have searched for proton decay via $p \rightarrow e^{+} \pi^{0}$ and \mu^{+} using Super-Kamiokande data from April 1996 to March 2015, 0.306 megaton$\cdot$years exposure in total. The atmospheric neutrino background rate IV is reduced almost half that of phase I-III by tagging neutrons associated with interactions. reach the lifetime further enhanced introducing new signal criteria select a hydrogen atom. No candidates were seen search. Two passed all selection been observed, but these...
The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance disappearance channels. This result comes from an exposure $14.9(16.4)\ifmmode\times\else\texttimes\fi{}1{0}^{20}$ protons on target in (antineutrino) mode. Significant improvements have been made to the interaction model far detector reconstruction. An extensive set simulated data studies also performed quantify effect uncertainties oscillation parameter sensitivity. performs...