研究者業績
基本情報
経歴
9-
2022年4月 - 現在
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2019年3月 - 2022年3月
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2016年7月 - 2019年2月
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2014年8月 - 2016年6月
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2013年10月 - 2014年7月
学歴
2-
1998年8月 - 2004年5月
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1994年4月 - 1998年3月
論文
352-
The Astrophysical Journal 937(2) 108-108 2022年10月1日Abstract Transient sources such as supernovae (SNe) and tidal disruption events are candidates of high-energy neutrino sources. However, SNe commonly occur in the universe and a chance coincidence of their detection with a neutrino signal cannot be avoided, which may lead to a challenge of claiming their association with neutrino emission. In order to overcome this difficulty, we propose a search for ∼10–100 TeV multiple neutrino events within a timescale of ∼30 days coming from the same direction, called neutrino multiplets. We show that demanding multiplet detection by a ∼1 km3 neutrino telescope limits the distances of detectable neutrino sources, which enables us to identify source counterparts by multiwavelength observations owing to the substantially reduced rate of the chance coincidence detection of transients. We apply our results by constructing a feasible strategy for optical follow-up observations and demonstrate that wide-field optical telescopes with a ≳4 m dish should be capable of identifying a transient associated with a neutrino multiplet. We also present the resultant sensitivity of multiplet neutrino detection as a function of the released energy of neutrinos and burst rate density. A model of neutrino transient sources with an emission energy greater than a few × 1051 erg and a burst rate rarer than a few ×10−8 Mpc−3 yr−1 is constrained by the null detection of multiplets by a ∼1 km3 scale neutrino telescope. This already disfavors the canonical high-luminosity gamma-ray bursts and jetted tidal disruption events as major sources in the TeV-energy neutrino sky.
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2022年1月29日We present a measurement of the density of GeV muons in near-vertical air showers using three years of data recorded by the IceTop array at the South Pole. Depending on the shower size, the muon densities have been measured at lateral distances between 200 m and 1000 m. From these lateral distributions, we derive the muon densities as functions of energy at reference distances of 600 m and 800 m for primary energies between 2.5 PeV and 40 PeV and between 9 PeV and 120 PeV, respectively. The muon densities are determined using, as a baseline, the hadronic interaction model Sibyll 2.1 together with various composition models. The measurements are consistent with the predicted muon densities within these baseline interaction and composition models. The measured muon densities have also been compared to simulations using the post-LHC models EPOS-LHC and QGSJet-II.04. The result of this comparison is that the post-LHC models together with any given composition model yield higher muon densities than observed. This is in contrast to the observations above 1 EeV where all model simulations yield for any mass composition lower muon densities than the measured ones. The post-LHC models in general feature higher muon densities so that the agreement with experimental data at the highest energies is improved but the muon densities are not correct in the energy range between 2.5 PeV and about 100 PeV.
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2022年1月18日For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data is provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above $\sim$50 EeV is provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrinos clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses has found a significant excess, and previously reported over-fluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs.
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2022年1月10日We report a search for nonstandard neutrino interactions (NSI) using eight years of TeV-scale atmospheric muon neutrino data from the IceCube Neutrino Observatory. By reconstructing incident energies and zenith angles for atmospheric neutrino events, this analysis presents unified confidence intervals for the NSI parameter $\epsilon_{\mu \tau}$. The best-fit value is consistent with no NSI at a p-value of 25.2%. With a 90% confidence interval of $-0.0041 \leq \epsilon_{\mu \tau} \leq 0.0031$ along the real axis and similar strength in the complex plane, this result is the strongest constraint on any NSI parameter from any oscillation channel to date.
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INTERNATIONAL JOURNAL OF COSMETIC SCIENCE 43(6) 653-661 2021年12月Objective It is known that damaged hair has a part of its internal structure damaged, and its water absorption and desorption behavior are different. In recent years, it has been reported that internal lipids play an important role in the adsorption and desorption of water to the hair. Therefore, we investigate whether the water distribution in hair and the amount of internal lipids are related. Methods To investigate the effect of internal lipid on water distribution, we prepare human hair samples with and without a partial lack of internal lipids. Internal lipids have been removed using formic acid. The distribution of D2O in the hair is investigated using small angle neutron scattering (SANS) under the wet and dry conditions of each hair sample. Results It is found from the obtained SANS data that formic acid-treated hairs tended to have fewer 40 angstrom-sized water clusters that were periodically present along the fibre axis in the wet condition. On the other hand, in the dry condition, there were no differences in water distribution between samples. Conclusion These observations are believed to have been caused by the reduction of 40 angstrom-sized water clusters existing on the constituents removed by formic acid treatment, especially the hydrophobic (lipid) constituent tissues. Consequently, it is clarified that internal lipids are deeply involved in the state of water distribution on hair in wet conditions.
MISC
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2023年8月18日The IceCube Neutrino Observatory, a cubic-kilometer-scale neutrino detector at the geographic South Pole, has reached a number of milestones in the field of neutrino astrophysics: the discovery of a high-energy astrophysical neutrino flux, the temporal and directional correlation of neutrinos with a flaring blazar, and a steady emission of neutrinos from the direction of an active galaxy of a Seyfert II type and the Milky Way. The next generation neutrino telescope, IceCube-Gen2, currently under development, will consist of three essential components: an array of about 10,000 optical sensors, embedded within approximately 8 cubic kilometers of ice, for detecting neutrinos with energies of TeV and above, with a sensitivity five times greater than that of IceCube; a surface array with scintillation panels and radio antennas targeting air showers; and buried radio antennas distributed over an area of more than 400 square kilometers to significantly enhance the sensitivity of detecting neutrino sources beyond EeV. This contribution describes the design and status of IceCube-Gen2 and discusses the expected sensitivity from the simulations of the optical, surface, and radio components.
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2022年12月30日The D-Egg, an acronym for ``Dual optical sensors in an Ellipsoid Glass for Gen2,'' is one of the optical modules designed for future extensions of the IceCube experiment at the South Pole. The D-Egg has an elongated-sphere shape to maximize the photon-sensitive effective area while maintaining a narrow diameter to reduce the cost and the time needed for drilling of the deployment holes in the glacial ice for the optical modules at depths up to 2700 meters. The D-Egg design is utilized for the IceCube Upgrade, the next stage of the IceCube project also known as IceCube-Gen2 Phase 1, where nearly half of the optical sensors to be deployed are D-Eggs. With two 8-inch high-quantum efficiency photomultiplier tubes (PMTs) per module, D-Eggs offer an increased effective area while retaining the successful design of the IceCube digital optical module (DOM). The convolution of the wavelength-dependent effective area and the Cherenkov emission spectrum provides an effective photodetection sensitivity that is 2.8 times larger than that of IceCube DOMs. The signal of each of the two PMTs is digitized using ultra-low-power 14-bit analog-to-digital converters with a sampling frequency of 240 MSPS, enabling a flexible event triggering, as well as seamless and lossless event recording of single-photon signals to multi-photons exceeding 200 photoelectrons within 10 nanoseconds. Mass production of D-Eggs has been completed, with 277 out of the 310 D-Eggs produced to be used in the IceCube Upgrade. In this paper, we report the des\ ign of the D-Eggs, as well as the sensitivity and the single to multi-photon detection performance of mass-produced D-Eggs measured in a laboratory using the built-in data acquisition system in each D-Egg optical sensor module.
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日本物理学会誌 76(10) 626-627 2021年<p>最近のトピックス</p><p>IceCubeニュートリノ望遠鏡によるグラショウ共鳴反応の観測</p>
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Proceedings of Science 30-July-2015 2015年11月12日This report is the write-up of a rapporteur talk on neutrino astronomy given at the 34th International Cosmic Ray Conference in The Hague, Netherlands, in 2015. Here, selected contributions on the neutrino astronomy from the total of 40 talks and 90 posters presented in NU sessions at the 34th ICRC are summarized in the attempt of providing a status report on this rapidly glowing new field. The field of neutrino astronomy has recently experienced a "phase transition" since the first observation of high energy cosmic neutrinos. Extensive efforts have been made to identify the origin of the neutrino flux observed in the 100 TeV to PeV region, from both theoretical and experimental perspectives. In addition, the search for neutrino fluxes beyond the observed level has become increasingly important for further understanding the origin of the observed cosmic-ray up to $10^{20}$ eV. Although the IceCube Neutrino Observatory is the only experiment currently measuring this neutrino flux, its initial measurements have been confirmed via analysis using several independent detection channels. Further, there have been a number of developments in the search for neutrino point sources, while no successful observations have yet been reported. Following the IceCube observations, a large number of studies of next-generation neutrino detectors, including up-scaled underground Cherenkov neutrino detectors and Cherenkov radio neutrino detectors, have been reported.
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日本物理学会誌 68(11) 738-743 2013年高エネルギーニュートリノは,遠い宇宙に存在する莫大なエネルギーの放出を伴う天体で作られる.この高エネルギー宇宙ニュートリノを検出し,その分布及び発生源を特定することによってニュートリノ天文学を確立することが,IceCube(アイスキューブ)実験の目的である.2011年8月と2012年1月, 1PeV(=1GeVの百万倍)を超えるエネルギーのニュートリノ現象がIceCubeによって高い信頼度で検出された.この高エネルギーニュートリノ事象の発見により,ニュートリノ天文学が大きく進展している.
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ASTROPARTICLE PHYSICS 26(4-5) 282-300 2006年11月The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN models, as briefly reviewed in this paper. The source stacking search for neutrinos from generic AGN classes is illustrated using the data collected by the AMANDA-II highenergy neutrino detector during the year 2000. No significant excess for any of the suggested groups was found. (c) 2006 Elsevier B.V. All rights reserved.
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ASTROPARTICLE PHYSICS 26(3) 155-173 2006年10月The first sensors of the IceCube neutrino observatory were deployed at the South Pole during the austral summer of 2004-2005 and have been producing data since February 2005. One string of 60 sensors buried in the ice and a surface array of eight ice Cherenkov tanks took data until December 2005 when deployment of the next set of strings and tanks began. We have analyzed these data, demonstrating that the performance of the system meets or exceeds design requirements. Times are determined across the whole array to a relative precision of better than 3 ns, allowing reconstruction of muon tracks and light bursts in the ice, of air-showers in the surface array and of events seen in coincidence by surface and deep-ice detectors separated by up to 2.5 km. (c) 2006 Elsevier B.V. All rights reserved.
共同研究・競争的資金等の研究課題
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