A5061072082- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Nuclear Physics and Applications
- Geophysics and Gravity Measurements
- Methane Hydrates and Related Phenomena
- Atomic and Subatomic Physics Research
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Radioactivity and Radon Measurements
- Earthquake Detection and Analysis
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Stellar, planetary, and galactic studies
- Radioactive contamination and transfer
- High-pressure geophysics and materials
- Electron and X-Ray Spectroscopy Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Detector Development and Performance
- Crystal Structures and Properties
- Magnetic Properties of Alloys
Tohoku University
2011-2024
The University of Tokyo
2016
Gakushuin University
2001
JEOL (Japan)
1990
The KamLAND-Zen experiment has provided stringent constraints on the neutrinoless double-beta (0νββ) decay half-life in ^{136}Xe using a xenon-loaded liquid scintillator. We report an improved search upgraded detector with almost double amount of xenon and ultralow radioactivity container, corresponding to exposure 970 kg yr ^{136}Xe. These new data provide valuable insight into backgrounds, especially from cosmic muon spallation xenon, have required use novel background rejection...
We report on a search for electron antineutrinos ($\bar{\nu}_e$) from astrophysical sources in the neutrino energy range 8.3 to 30.8 MeV with KamLAND detector. In an exposure of 6.72 kton-year liquid scintillator, we observe 18 candidate events via inverse beta decay reaction. Although there is large background uncertainty neutral current atmospheric interactions, find no significant excess over model predictions. Assuming several supernova relic spectra, give upper flux limits 60--110...
Abstract The electron antineutrino flux limits are presented for the brightest gamma-ray burst (GRB) of all time, GRB221009A, over a range 1.8–200 MeV using Kamioka Liquid Scintillator Antineutrino Detector. Using multiple time windows ranging from minutes to days surrounding event search antineutrinos coincident with GRB, we set an upper limit on under assumption several power-law neutrino source spectra, indices 1.5 3 in steps 0.5. No excess was observed any seconds around trigger T 0 ....
Abstract The decay of the primordial isotopes 238 U, 235 232 Th, and 40 K has contributed to terrestrial heat budget throughout Earth's history. Hence, individual abundance those are key parameters in reconstructing contemporary Earth models. geoneutrinos produced by radioactive decays uranium thorium have been observed with Kamioka Liquid‐Scintillator Antineutrino Detector (KamLAND). Those measurements improved more than 18‐year observation time, improvement detector background levels...
We report a measurement of the strange axial coupling constant ${g}_{A}^{s}$ using atmospheric neutrino data at KamLAND. This is component form factor neutral-current quasielastic (NCQE) interaction. The value significantly changes ratio proton and neutron NCQE cross sections. KamLAND suitable for measuring interactions as it can detect nucleon recoils with low-energy thresholds measure multiplicity high efficiency. data, including information on associated interactions, makes possible to...
We present a search for neutrinoless double-beta ($0\nu\beta\beta$) decay of $^{136}$Xe using the full KamLAND-Zen 800 dataset with 745 kg enriched xenon, corresponding to an exposure $2.097$ ton yr $^{136}$Xe. This updated benefits from more than twofold increase in exposure, recovery photo-sensor gain, and reduced background muon-induced spallation xenon. Combining previous phase, we obtain lower limit $0\nu\beta\beta$ half-life $T_{1/2}^{0\nu} > 3.8 \times 10^{26}$ at 90% C.L., factor 1.7...
Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-$\ensuremath{\beta}$ decay, and dark matter search experiments. The KamLAND-Zen experiment neutrinoless decay 745 kg of xenon dissolved liquid scintillator. includes dead-time-free electronics with a high efficiency detecting muon-induced neutrons. production yields different are measured combination delayed...
Abstract Preceding a core-collapse supernova (CCSN), various processes produce an increasing amount of neutrinos all flavors characterized by mounting energies from the interior massive stars. Among them, electron antineutrinos are potentially detectable terrestrial neutrino experiments such as KamLAND and Super-Kamiokande (SK) via inverse beta decay interactions. Once these pre-supernova (pre-SN) observed, early warning upcoming CCSN can be provided. In light this, SK, both located in...
Abstract We evaluated and measured the influence of channelling on changes in intensity characteristic lines background Auger electron spectra by performing calculations experiments an aluminium single crystal. Propagation incident beam crystal was calculated dynamic theory diffraction, while Monte‐Carlo method used to simulate paths material as a function experimental conditions. contrasts Al LVV (68 eV) KLL (1396 both abnormal absorption positions we recorded En(E) curves for different...
We report the result of a search for neutrinos in coincidence with solar flares from GOES flare database. The was performed on 10.8 kton-year exposure KamLAND collected 2002 to 2019. This large allows us explore previously unconstrained parameter space neutrinos. found no statistical excess and established 90% confidence level upper limits $8.4 \times 10^7$ cm$^{-2}$ ($3.0 10^{9}$ cm$^{-2}$) electron anti-neutrino (electron neutrino) fluence at 20 MeV normalized X12 flare, assuming that...
We present the results of a search for MeV-scale electron antineutrino events in KamLAND coincident with 60 gravitational wave events/candidates reported by LIGO/Virgo collaboration during their second and third observing runs. find no significant signals within $\pm$ 500 s timing window from each 90% C.L. upper limits on fluence between $10^{8}$-$10^{13}\,{\mathrm cm^2}$ neutrino energies energy range 1.8-111 MeV.
We present the results of a search for core-collapse supernova neutrinos, using long-term KamLAND data from 2002 March 9 to 2020 April 25. focus on electron antineutrinos emitted supernovae in energy range 1.8--111 MeV. Supernovae will make neutrino event cluster with duration $\sim$10 s data. find no clusters and give upper limit rate as be 0.15 yr$^{-1}$ 90% confidence level. The detectable range, which corresponds >95% detection probability, is 40--59 kpc 65--81 failed supernovae,...
We present the results of a time-coincident event search for low-energy electron antineutrinos in KamLAND detector with gamma-ray bursts from Gamma-ray Coordinates Network and Fermi Burst Monitor. Using variable coincidence time window $\pm$500s plus duration each burst, no statistically significant excess above background is observed. place world's most stringent 90% confidence level upper limit on antineutrino fluence below 17.5 MeV. Assuming Fermi-Dirac neutrino energy spectrum burst...
Preceding a core-collapse supernova, various processes produce an increasing amount of neutrinos all flavors characterized by mounting energies from the interior massive stars. Among them, electron antineutrinos are potentially detectable terrestrial neutrino experiments such as KamLAND and Super-Kamiokande via inverse beta decay interactions. Once these pre-supernova observed, early warning upcoming supernova can be provided. In light this, have been monitoring since 2015 2021,...
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP (χ0) accompanied by negatively excited state (χ−) with small mass difference (e.g. < 20 MeV) can form bound-state nucleus such as xenon. This formation is rare and the released energy O(1−10) MeV depending on nucleus, making large liquid scintillator detectors suitable for detection. We searched events xenon in two experimental phases of KamLAND-Zen experiment, xenon-doped detector. No...
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP ($\chi^{0}$) accompanied by negatively excited state ($\chi^{-}$) with small mass difference (e.g. $<$ 20 MeV) can form bound-state nucleus such as xenon. This formation is rare and the released energy $\mathcal{O}(1-10$) MeV depending on nucleus, making large liquid scintillator detectors suitable for detection. We searched events xenon in two experimental phases of KamLAND-Zen experiment,...
An in situ synchrotron powder X‑ray diffraction study on (Fe0.89,Ni0.11)3S was conducted up to 141 GPa and 1590 K. has a tetragonal structure, which is the same structure as Ni-free Fe3S. Fitting third-order Birch-Murnaghan equation of state data at ambient temperature yielded bulk modulus K0 = 138.1(7.2) its pressure derivative K0′ 4.5(3) with zero volume V0 375.67(4) Å3. The density under core-mantle boundary condition 1.7% greater than that axial ratio (c/a) decreases increasing pressure....