- 著者
- 水谷 興平
- 出版者
- IOP PUBLISHING LTD
- 雑誌
- ASTROPHYSICAL JOURNAL (ISSN:0004637X)
- 巻号頁・発行日
- vol.692, no.1, pp.61-72, 2009-02
- 被引用文献数
- 49
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 gamma-rays from the Crab Nebula, expressed by a power law as (dJ/dE) = (2.09 +/- 0.32) x 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 gamma-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 0 degrees.011. 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.
- 著者
- Hase Muneaki Katsuragawa Masayuki Constantinescu Anca Monia Petek Hrvoje
- 出版者
- IOP Publishing Ltd
- 雑誌
- New journal of physics (ISSN:13672630)
- 巻号頁・発行日
- vol.15, no.5, pp.055018, 2013-05
- 被引用文献数
- 21 2
The coherent modulation of electronic and vibrational nonlinearities in atoms and molecular gases by intense few-cycle pulses has been used for high-harmonic generation in the soft x-ray and attosecond regime, as well as for Raman frequency combs that span multiple octaves from the terahertz to petahertz frequency regions. In principle, similar high-order nonlinear processes can be excited efficiently in solids and liquids on account of their high nonlinear polarizability densities. In this paper, we demonstrate the phononic modulation of the optical index of Si and GaAs for excitation and probing near their direct band gaps, respectively at ~3.4 and ~3.0 eV. The large amplitude coherent longitudinal optical (LO) polarization due to the excitation of LO phonons of Si (001) and LO phonon–plasmon coupled modes in GaAs (001) excited by 10 fs laser pulses induces effective amplitude and phase modulation of the reflected probe light. The combined action of the amplitude and phase modulation in Si and GaAs generates phonon frequency combs with more than 100 and 60 THz bandwidth, respectively.
- 著者
- Umeda T Ohno H Kanaya K
- 出版者
- IOP Publishing Ltd
- 雑誌
- Journal of physics. G, Nuclear and particle physics (ISSN:09543899)
- 巻号頁・発行日
- vol.35, no.10, pp.104157, 2008-10
- 被引用文献数
- 1 1
Dissociation temperatures of J/ψ, ψ' and χc states play key roles in the sequential J/ψ suppression scenario for high-energy heavy-ion collisions. We report on a study of charmonium dissociation temperatures in quenched lattice QCD. On anisotropic lattices, we first subtract the effects of the constant mode in finite temperature meson correlators, which have led to unphysical results in previous studies. We then extract ground and first exited state masses by diagonalizing correlation functions among different source and sink operators. To distinguish bound states from scattering states, we first compare the charmonium mass spectra under different spatial boundary conditions, and examine the shape and the volume dependence of their Bethe–Salpeter wavefunctions. From these studies, we found, so far, no sign of scattering states up to about 2.3Tc.
- 著者
- Ohno H Umeda T Kanaya K WHOT-QCD Collaboration
- 出版者
- IOP Publishing Ltd
- 雑誌
- Journal of physics. G, Nuclear and particle physics (ISSN:09543899)
- 巻号頁・発行日
- vol.36, no.6, pp.064027, 2009
- 被引用文献数
- 4
Dissociation of charmonia in hot QCD is studied on a quenched anisotropic lattice using standard plaquette gauge action and O(a) improved Wilson fermion action. Simulations are carried out at temperatures in the range 0.88 TC to 2.3 TC. We calculate effective masses and Bethe–Salpeter wavefunctions for the ground state (1S, 1P) and some excited states (2S, 2P) with variational analysis. To distinguish between bound states and scattering states, we apply two methods: first, we compare effective masses for charmonium correlation functions under different spatial boundary conditions. Because the scattering states are sensitive to the boundary conditions, finite volume effects are expected when a charmonium dissociates. Second, we study if the wavefunctions show a sign of scattering states which will be characterized by a broad wavefunction. We find no clear evidence of dissociation for the charmonium states up to 2.3 TC so far.