Mitsuhiro Teshima

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A new type of Hybrid PhotoDetectors (HPDs) with an 18-mm-diameter GaAsP photo cathode was developed in order to lower the energy threshold of the MAGIC-II project down to 15 GeV. The peak value of the Quantum Efficiency (QE) of these novel sensors reaches ~ 50 % at around 500 nm. Application of the wavelength shifting technique can further enhance the(More)
  • M Takeda, N Hayashida, K Honda, N Inoue, K Kadota, F Kakimoto +23 others
  • 1999
With the Akeno Giant Air Shower Array (AGASA), 581 cosmic rays above 10 19 eV, 47 above 4 × 10 19 eV, and 7 above 10 20 eV are observed until August 1998. Arrival direction distribution of these extremely high energy cosmic rays has been studied. While no significant large-scale anisotropy is found on the celestial sphere, some interesting clusters of(More)
  • M Takeda, N Hayashida, K Honda, N Inoue, K Kadota, F Kakimoto +22 others
  • 1998
The cosmic-ray energy spectrum above 10 18.5 eV is reported using the updated data set of the Akeno Giant Air Shower Array (AGASA) from February 1990 to October 1997. The energy spectrum extends beyond 10 20 eV and the energy gap between the highest energy event and the others is being filled up with recently observed events. The spectral shape suggests the(More)
One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts. In(More)
We measured the air uorescence yield as a function of pressure with electrons between 1.4 MeV and 1000 MeV by means of a 90 Sr source and an electron beam. Results indicate that the uorescence yield is proportional to electron energy loss from 1.4 MeV to 1000 MeV. The dE dx relativistic rise in air is detected. We describe the pressure temperature(More)
The nearby dwarf spheroidal galaxy Draco with its high mass to light ratio is one of the most auspicious targets for indirect dark matter (DM) searches. Annihilation of hypothetical DM particles can result in high-energy γ-rays, e.g. from neutralino annihilation in the supersymmetric framework. With the MAGIC telescope a search for a possible DM signal(More)
We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index ≃ 1 + (E/M QGn) n , n = 1, 2. Parametrizing the delay between γ-rays of different energies as ∆t = ±τ l E(More)
The Cherenkov light flashes produced by Extensive Air Showers are very short in time. A high bandwidth and fast digitizing readout, therefore, can minimize the influence of the background from the light of the night sky, and improve the performance in Cherenkov telescopes. The time structure of the Cherenkov image can further be used in single-dish(More)
The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy(More)
  • M Takeda, N Sakaki, K Honda, M Chikawa, M Fukushima, N Hayashida +26 others
  • 2002
Using data from more than ten-years of observations with the Akeno Giant Air Shower Array (AGASA), we published a result that the energy spectrum of ultra-high energy cosmic rays extends beyond the cutoff energy predicted by Greisen [1], and Zatsepin and Kuzmin [2]. In this paper, we reevaluate the energy determination method used for AGASA events with(More)