# T. Yuda's research while affiliated with The University of Tokyo and other places

## Publications (289)

Article
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The CALorimetric Electron Telescope (CALET), launched for installation on the International Space Station (ISS) in August, 2015, has been accumulating scientific data since October, 2015. CALET is intended to perform long-duration observations of high-energy cosmic rays onboard the ISS. CALET directly measures the cosmic-ray electron spectrum in th...
Article
We analyze the Sun’s shadow observed with the Tibet-III air shower array and find that the shadow’s center deviates northward (southward) from the optical solar disk center in the “away” (“toward”) interplanetary magnetic field (IMF) sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IM...
Article
Full-text available
First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical th...
Article
Full-text available
In August 2015, the CALorimetric Electron Telescope (CALET), designed for long exposure observations of high energy cosmic rays, docked with the International Space Station (ISS) and shortly thereafter began to collect data. CALET will measure the cosmic ray electron spectrum over the energy range of 1 GeV to 20 TeV with a very high resolution of 2...
Article
We report on the analysis of the 10-1000 TeV large-scale sidereal anisotropy of Galactic cosmic rays (GCRs) with the data collected by the Tibet Air Shower Array from 1995 October to 2010 February. In this analysis, we improve the energy estimate and extend the decl. range down to -30°. We find that the anisotropy maps above 100 TeV are distinct fr...
Article
We present upper limits in the hard X-ray and gamma-ray bands at the time of the LIGO gravitational-wave event GW 151226 derived from the CALorimetric Electron Telescope (CALET) observation. The main instrument of CALET, CALorimeter (CAL), observes gamma-rays from ~1 GeV up to 10 TeV with a field of view of ~2 sr. The CALET gamma-ray burst monitor...
Article
A 100 m2 muon detector (MD) was successfully constructed under the existing Tibet air shower (AS) array in the late fall of 2007. The sensitivity of the Tibet AS array to cosmic gamma rays can be improved by selecting muon-poor events with the MD. Our MC simulation of the MD response reasonably agrees with the experimental data in terms of the char...
Data
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Article
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The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bu...
Article
Full-text available
The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bu...
Article
The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bu...
Article
The CALorimetric Electron Telescope (CALET) space experiment, currently under development by Japan in collaboration with Italy and the United States, will measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma rays to 10 TeV and nuclei with Z=1 to 40 up to 1,000 TeV during a two-year mission on the International Space Stati...
Article
We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the Potential Field Source S...
Article
In this paper, we report solar neutron events detected in the solar cycle 23, especially three interesting events detected on November 23rd and 28th 1998 in Tibet and October 28th 2003 in Tsumeb.
Article
Using the Tibet-III air shower array, we search for steady TeV γ-rays from 18 pulsars in the Fermi Large Area Telescope pulsar catalog. Among them, we observe 8 sources including the Crab instead of the expected 0.41 sources at a significance of 2 σ or more excess. Under the assumption of Poisson distribution, the chance probability is estimated to...
Article
The Tibet AS-gamma collaboration is constructing 4500 m2 underground muon detector array by using water Cherenkov technique, to form the TIBET AS+MD hybrid array. The muon detector will improve the sensitivity of gamma ray and electron observation above 10 TeV by rejecting the cosmic ray background. In TIBET AS+MD, both water-recycling system and c...
Article
The galactic cosmic-ray anisotropy at TeV energies has a large-scale deficit region distributed around 150 to 240 degrees in right ascension, which is called "Loss-Cone". The Milagro experiment in the U.S. detected a significant increase in the Loss-Cone amplitude at 6 TeV from July 2000 to July 2007, and argued that it could be due to variations i...
Article
We have operated the 500 m2 Yangbajing air-shower core (YAC-II) detector array near the center of the Tibet air-shower array ( Tibet-III ) to study the cosmic-ray chemical composition at the knee energy region since August, 2011. YAC-II array consists of 124 YAC detector units. Each unit of YAC-II consists of a lead layer of 3.5 cm thick and a scin...
Article
A possible origin of the large-scale anisotropy of TeV galactic cosmic rays is discussed. It can be well modeled by a superposition of the Global Anisotropy and the Midscale Anisotropy. The Global Anisotropy would be generated by galactic cosmic rays interacting with the magnetic field in the local interstellar space of a few parsec scale surroundi...
Article
New air-shower core detector YAC has been developed to measure cosmic-ray mass composition around the energy region of the knee. Prototype experiment YAC1 was successfully carried out in 2009-2010 together with Tibet III air-shower array. Enlarged installation YAC2 is also under construction and will be operated in fall 2011. Preliminary result of...
Article
Aiming at the observation of cosmic-ray chemical composition at the knee energy region, a new type airshower- core detector (YAC, Yangbajing Air shower Core array) has been developed and set up at Yangbajing, 4300 m a.s.l. in Tibet, China since August, 1st, 2011. YAC will work together with the Tibet-III array and a large muon detector as a hybrid...
Article
A hybrid experiment has been started by ASγ collaboration at Tibet, China, since May 2009, that consists of a burst-detector-grid (YAC, Yangbajing Air shower Core array) and the Tibet air-shower array (Tibet-III). The first step of YAC, called YAC-I, contains 16 detector units and observes high energy electromagnetic particles in air-shower cores w...
Article
We are now operating the 500 m2 Yangbajing air-shower core (YAC-II) array near the center of the Tibet air-shower array ( Tibet-III ) to observe cosmic-ray chemical composition at the knee energy region since February 2011. The first step of YAC, called YAC-I, containing 16 detector units, was operated from May, 2009 to February, 2010. In this pape...
Article
We analyze the solar cycle variation of the Sun's shadow in 10 TeV cosmic ray intensity observed with the Tibet air shower array over an entire period of the Solar Cycle 23 between 1996 and 2008. The amplitude of the variation is as large as one half of the deficit intensity expected when all cosmic rays arriving from the direction of the optical S...
Article
There are various explanations about the origin of lightning during thunderstorms. A possible explanation is that the cosmic rays may be caused of triggers of lightning. In order to measure any correlations between atmospheric charged particles and atmospheric electric field, we have installed some atmospheric electric field meter inside the Tibet...
Article
A new hybrid experiment has been started by ASγ experiment at Tibet, China, since August 2011, which consists of a low threshold burst-detector-grid (YAC-II, Yangbajing Air shower Core array), the Tibet air-shower array (Tibet-III) and a large underground water Cherenkov muon detector (MD). In this paper, the capability of the measurement of the ch...
Article
We are now proposing the 10,000m2 water-Cherenkov-type muon detector (MD) array under the Tibet air shower (AS) array to find new gamma-ray sources with a wide field of view and unprecedented flux sensitivity. In the late fall of 2007, a prototype MD in area of 100m2 was constructed under the existing Tibet AS array. In this paper, we search for su...
Article
We plan to build a large (approximately 10,000 m2) water-Cherenkov-type muon detector array under the existing Tibet air shower array at 4,300 m above sea level, to observe 10-1000 TeV gamma rays from cosmic-ray accelerators in our Galaxy with wide field of view at very low background level. The gamma-ray induced air shower has significantly less m...
Article
The energy spectrum of cosmic rays around the knee measured by Tibet air-shower experiment is summarized and its characteristic features are discussed under two possible scenarios. The result of Tibet experiment measured over wide range of 1014-1017 eV with high statistics provided details of the knee at the energy around 4×1015 eV. The study of th...
Article
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We analyze the large-scale two-dimensional sidereal anisotropy of multi-TeV cosmic rays by Tibet Air Shower Array, with the data taken from 1999 November to 2008 December. To explore temporal variations of the anisotropy, the data set is divided into nine intervals, each in a time span of about one year. The sidereal anisotropy of magnitude about 0...
Article
Full-text available
Using the Tibet-III air shower array, we search for TeV gamma-rays from 27 potential Galactic sources in the early list of bright sources obtained by the Fermi Large Area Telescope at energies above 100 MeV. Among them, we observe 7 sources instead of the expected 0.61 sources at a significance of 2 sigma or more excess. The chance probability from...
Article
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We develop a model anisotropy best-fitting to the two-dimensional sky-map of multi-TeV galactic cosmic ray (GCR) intensity observed with the Tibet III air shower (AS) array. By incorporating a pair of intensity excesses in the hydrogen deflection plane (HDP) suggested by Gurnett et al., together with the uni-directional and bi-directional flows for...
Article
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The Tibet-III air shower array, consisting of 533 scintillation detectors, has been operating successfully at Yangbajing in Tibet, China since 1999. Using the data set collected by this array from 1999 November through 2005 November, we obtained the energy spectrum of γ-rays from the Crab Nebula, expressed by a power law as (dJ/dE) = (2.09 ± 0.32)...
Article
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We report the observations of TeV gamma-ray flares from Markarian 501 using the Telescope Array Prototype. The observations were carried out continuously from the end of March to the end of July of 1997. The energy spectrum and the time variation of the gamma-ray intensities are shown. The intensity has been changed by an order of magnitude in this...
Article
The Tibet-III air shower array, consisting of 789 scintillation detectors, has been operating successfully at Yangbajing in Tibet since 1999. Some recent results on gamma-ray observation by the Tibet-III air shower array are introduced and its future prospects of gamma-ray observation will be discussed.
Article
Recent results and future prospects of the Tibet air-shower experiment are reported on the all-particle energy spectrum and the chemical composition of cosmic rays around 1015eV energy range. The knee of the all-particle energy spectrum has been clearly observed at the energy around 4x1015eV by Tibet III air-shower array located at Yangbajing, Tibe...
Article
The Tibet-III air shower array, consisting of 789 scintillation detectors, has been operating successfully at Yangbajing in Tibet since 1999. Some recent results on gamma-ray observation by the Tibet-III air shower array are introduced and its future prospects of gamma-ray observation will be discussed.
Article
A network of solar neutron telescopes has been developed since the middle of solar cycle 22. We have detected several important solar neutron events until the end of solar cycle 23 using solar neutron telescopes, but the accumulation of more solar neutron events is indispensable to eclucidate the acceleration mechanism of high energy particles. The...
Article
We have analyzed the large scale sidereal anisotropy of multi-TeV Galactic cosmic rays by Tibet Air Shower Array, with the data taken from Nov. 1999 to Nov. 2005. To study the temporal variation of the anisotropy, the data set is divided into 6 samples, each in a time scale of one year.It is shown that the sidereal anisotropy with the magnitude abo...
Article
The solar activity is gradually changing from the Solar Cycle 23 to 24. Sun's shadow generated by multi-TeV cosmic-ray particles has been continuously observed with the Tibet-II and Tibet- III air shower array in 1996 through 2008. We have shown that the Sun's shadow is strongly affected by the solar and interplanetary magnetic fields changing with...
Article
We carried out electron observations with balloons to investigate acceleration and propagation of electrons in the universe. We developed BETS (Balloon-borne Electron Telescope with Scintillation fibers) for electron observations in Sanriku. We obtained electron energy spectrum from 10 GeV to 100 GeV with it. At higher energies, the energy spectrum...
Article
Results of a steady TeV γ-ray point-source search using data taken from the Tibet HD (1997 February-1999 September) and Tibet III (1999 November-2001 October) arrays are presented. From 0° to 60° in declination, significant excesses from the well-known steady source Crab Nebula and the high state of the flare-type source Markarian 421 are observed....
Article
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We searched for steady PeV gamma-ray emission from the Monogem ring region with the Tibet air shower array from 1997 February to 2004 October. No evidence for statistically significant gamma-ray signals was found in a region 111° ≤ R.A. < 114°, 125 ≤ decl. < 155 in the Monogem ring where the MAKET-ANI experiment recently claimed a positive detectio...
Article
Several strong TeV γ-ray flares were detected from Mrk 421 in the years 2000 and 2001 by the Tibet III air shower array at a level of statistical significance of 5.1 σ. Mrk 421 was unprecedentedly active at X-ray and TeV γ-ray energies during this period, and a positive correlation was found between the change of the all-sky monitor Rossi X-Ray Tim...
Article
Cosmic-ray electrons have been observed in the energy region from 10 GeV to 1 TeV with the PPB-BETS by a long duration balloon flight using a Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an average altitude of 35 km in January 2004. The PPB-BETS detector is an imaging calorimeter composed of scintillating...
Article
Full-text available
We have observed cosmic-ray electrons from 10 GeV to 800 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an average altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted be...
Article
The Tibet air shower array, which has an effective area of 36,900 m2, has been in operation at Yangbajing in Tibet, China at an altitude of 4,300 m above sea level. In this paper, we will briefly introduce the recent gamma-ray observation with the present Tibet air shower array and our future plan which is called the Tibet muon detector (MD) projec...
Article
We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10(14) to 10(17) eV using 5.5 x 107 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m above sea level (an atmospheric depth of 606 g cm(-2)). The size spectrum exhibits a sharp knee at a correspondin...
Article
The CALorimetric Electron Telescope, CALET, is a new Space Observatory being developed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electron spectrum from 10's of Ge...
Article
The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The scientific objective is to investigate the origin of the cosmic electrons and gamma-rays in very high energy region. The detector is composed of an imaging calorimeter of scintillating...
Article
We report on the spectral index of cosmic rays around 10 TeV energy region obtained by observation of the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun with the Tibet III air shower array during the period from 1999 to 2005. The spectral index has turned out to be 2.99±0.54, which is consistent with 2.74 by the dir...
Article
We searched for steady 100 TeV gamma-ray point sources from -10° to +70° in declination based on six year data obtained from Nov. 1999 to Nov. 2005 by the Tibet air shower array. No new source was found and no significant excess of events could be detected from known TeV sources. We set flux upper limits above 100 TeV on several nearby objects loca...
Article
Full-text available
The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We have a plan to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV energy re...
Article
Full-text available
The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We are planning to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV (10 - 10...
Article
Full-text available
The amplitude of the Compton-Getting (CG) anisotropy contains the power-law index of the cosmic-ray energy spectrum. Based on this relation and using the Tibet air-shower array data, we measure the cosmic-ray spectral index to be $-3.03 \pm 0.55_{stat} \pm < 0.62_{syst}$ between 6 TeV and 40 TeV, consistent with $-$2.7 from direct energy spectrum m...
Article
We have observed the shadowing of galactic cosmic ray flux in the direction of the moon, the so-called moon shadow, using the Tibet-III air shower array operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic rays are positively charged; for that reason, they are bent by the geomagnetic field, thereby shifting the moon shadow...
Article
A new solar neutron telescope has been constructed at Yangbajing, Tibet (600 g/cm2) and has been successfully operated for 8 years. During this time several interesting events were observed in coincidence with large solar flares. In this paper the authors discuss a directional count rate enhancement 1998 November 28 as to whether it is related to s...
Article
We show that the large‐scale anisotropy of ∼5 TeV galactic cosmic ray (GCR) intensity observed by Tibet Air Shower experiment can be reproduced by the superposition of a bi‐directional and uni‐directional flows (UDF and BDF) of GCRs. The heliosphere is located inside the local interstellar cloud (LIC) very close to the inner edge of the LIC. If th...
Article
Gigantic solar flares exceeding X-class occurred 10 times in September, 2005, and 4 times in December, 2006, although the Sun had already been in the declining phase in solar cycle 23. In this paper, we report on results of the search for solar neutron events associated with these 14 X-class flares, using data obtained by the international network...
Article
We have observed cosmic-ray electrons from 10 GeV to 1 TeV with PPB-BETS by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserte...
Article
Full-text available
We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 10 TeV and rays in 20 MeV...
Article
We have observed cosmic-ray electrons from 10 to 1000 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead...
Article
Simultaneous observation of γ-families and their accompanying air showers was performed at Yangbajing (4300 m above sea level) in Tibet with the emulsion chambers and burst detectors which were linked with the Tibet-II air-shower array. For three years operation, we observed 177 γ-families (∑Eγ > 20 TeV) accompanying air showers with the size Ne >...
Article
According to many solar observations, the solar activity, during the Solar Cycle 23, is gradually declining to the quiet phase from the high state in 2000–2004. The Tibet air shower array has been continuing the observation of the shadow that cosmic rays make in the 0273-1177/\$30 Ó direction of the sun or the moon since 1991. We have shown the infl...
Article
The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details...
Article
Full-text available
The Tibet hybrid experiment composed of emulsion chambers, burst detectors and the Tibet-II air-shower array was done at Yangbajing (4,300m above sea level, 606 g/cm2) in Tibet. For 3-year operation, we have observed 177 gamma-families (SigmaEgamma > 20 TeV) accompanying air showers with the shower size Ne > 2 × 105. Using this data set and a neura...
Chapter
The Long-Term variation of the solar diurnal anisotropy of the galactic cosmic ray intensity in the Sub-TeV region is studied by using data recorded over 20 years with the deep underground muon detector at Matsushiro in Japan since 1984. The harmonic dial of the diurnal variation shows a clear 11-Year change. At around 1987 and 1998, the variation...
Article
We obtained new upper limits on the diffuse gamma rays from the inner Galactic (IG) and outer Galactic (OG) planes in 3–10 TeV region, using the Tibet air shower data and new Monte Carlo simulation results. A difference of the effective area of the air-shower array for observing gamma rays and cosmic rays was carefully taken into account in this an...
Article
A hybrid experiment consisting of emulsion chambers, burst detectors and the Tibet-II air-shower array was carried out at Yangbajing (4300 m a.s.l., 606 g/cm2) in Tibet to obtain the energy spectra of primary protons and heliums. From three-year operation, these energy spectra are deduced between 10 15 and 1016 eV by triggering the air showers asso...
Article
Full-text available
In this paper, we report solar neutron events detected in the solar cycle 23, especially three interesting events detected on November 23rd and 28th 1998 in Tibet and October 28th 2003 in Tsumeb.