Showing papers by "S. L. Lu published in 2009"
Hirosaki University1, Chinese Academy of Sciences2, University of Tokyo3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, Konan University11, Waseda University12, Yokohama National University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, Sakushin Gakuin University18, College of Industrial Technology19, Max Planck Society20, Shonan Institute of Technology21
TL;DR: In this article, the authors estimate the systematic error in determining the primary energy from its shower size, which is estimated to be less than ±12% in their experiment. But this error is consistent with other independent γ-ray observations by imaging air Cherenkov telescopes.
Abstract: 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) × 10–12(E/3 TeV)–2.96±0.14 cm–2 s–1 TeV–1 in the energy range of 1.7-40 TeV. This result is consistent with other independent γ-ray observations by imaging air Cherenkov telescopes. In this paper, we carefully checked and tuned the performance of the Tibet-III array using data on the Moon's shadow in comparison with a detailed Monte Carlo (MC) simulation. The shadow is shifted to the west of the Moon's apparent position as an effect of the geomagnetic field, although the extent of this displacement depends on the primary energy of positively charged cosmic rays. This finding enables us to estimate the systematic error in determining the primary energy from its shower size. This error is estimated to be less than ±12% in our experiment. This energy scale estimation is the first attempt among cosmic ray experiments at ground level. The systematic pointing error is also estimated to be smaller than 0011. The deficit rate and the position of the Moon's shadow are shown to be very stable within a statistical error of ±6% year by year. This guarantees the long-term stability of pointlike source observation with the Tibet-III array. These systematic errors are adequately taken into account in our study of the Crab Nebula.
51 citations
Hirosaki University1, Chinese Academy of Sciences2, University of Tokyo3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, Konan University11, Waseda University12, Yokohama National University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, Sakushin Gakuin University18, College of Industrial Technology19, Max Planck Society20, Shonan Institute of Technology21
TL;DR: In this paper, the knee of the all-particle energy spectrum has been clearly observed at the energy around 4 × 10 15 eV by Tibet III air-shower array located at Yangbajing, Tibet, China (atmospheric depth 606 g/cm 2, area 37,000 m 2 ).
Abstract: 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 10 15 eV energy range. The knee of the all-particle energy spectrum has been clearly observed at the energy around 4 ×10 15 eV by Tibet III air-shower array located at Yangbajing, Tibet, China (atmospheric depth 606 g/cm 2 , area 37,000 m 2 ). The energy spectrum of light components (protons and helium) measured by air-shower-core detector exhibits steeper power index than that of direct measurements below 10 14 eV, leading to decreasing fraction of the light component toward the knee. Hence, it is strongly suggested that the origin of the knee is related with the change of the chemical composition of cosmic rays. A new air-shower-core detector called `YAC' is under the preparation for explicit measurement of the heavy component.
3 citations
Hirosaki University1, University of Tokyo2, Hebei Normal University3, Tibet University4, Shandong University5, Southwest Jiaotong University6, Yunnan University7, Kanagawa University8, Utsunomiya University9, Konan University10, Waseda University11, Yokohama National University12, Shinshu University13, Chinese Academy of Sciences14, Tsinghua University15, Saitama University16, National Institute of Informatics17, Sakushin Gakuin University18, Max Planck Society19, Shonan Institute of Technology20, Nihon University21
TL;DR: In this article, a 10,000m2 water-Cherenkov-type muon detector (MD) array under the Tibet air shower (AS) array is proposed.
Abstract: We are planning to build a 10,000 m2 water‐Cherenkov‐type muon detector (MD) array under the Tibet air shower (AS) array. The Tibet AS+MD array will have the sensitivity to detect gamma rays in the 100 TeV region by an order of the magnitude better than any other previous existing detectors in the world. In the late fall of 2007, a prototype water Cherenkov muon detector of approximately 100 m2 was constructed under the existing Tibet AS array. The preliminary data analysis is in good agreement with our MC simulation. We are now ready for further expanding the underground water Cherenkov muon detector.
1 citations
Hirosaki University1, Chinese Academy of Sciences2, University of Tokyo3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, Konan University11, Waseda University12, Yokohama National University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, Sakushin Gakuin University18, College of Industrial Technology19, Max Planck Society20, Shonan Institute of Technology21
TL;DR: The Tibet-III air shower array, consisting of 789 scintillation detectors, has been operating successfully at Yangbajing in Tibet since 1999 as discussed by the authors, and its future prospects of gamma-ray observation are discussed.
Abstract: 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.
1 citations