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4 results on '"Y. Toi"'

1. Measurement of spin-density matrix elements forϕ-meson photoproduction from protons and deuterons near threshold

Author

M. Uchida, Y. Kato, J. K. Ahn, Hidetoshi Akimune, N. Matsuoka, W. C. Chang, M. Fujiwara, T. Matsumura, Masato Yoshimura, S. Daté, K. Yonehara, K. Horie, Tsutomu Mibe, Hiroyuki Toyokawa, H. Kawai, P. J. Lin, C. W. Wang, Takatsugu Ishikawa, S. Makino, Tetsuhiko Yorita, M. Niiyama, H. Ejiri, D. S. Oshuev, R. G. T. Zegers, Y. Toi, H. Fujimura, Y. Ohashi, S. C. Wang, Chary Rangacharyulu, T. Matsuda, Y. Miyachi, Takashi Nakano, A. Wakai, Y. Asano, K. Kino, K. Imai, Masaharu Nomachi, T. Ooba, D. S. Ahn, M. Sumihama, Y. Shiino, K. Hicks, M. Miyabe, S. Hasegawa, Haruo Ohkuma, Atsushi Sakaguchi, N. Kumagai, Tomoaki Hotta, Takahiro Iwata, P. M. Shagin, H. Kohri, Yorihito Sugaya, Hajime Shimizu, Norihito Muramatsu, Shuji Fukui, and M. Yosoi

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Nuclear Theory, Meson, High Energy Physics::Phenomenology, Hadron, Elementary particle, Pseudoscalar meson, Helicity, Nuclear physics, Baryon, Pseudoscalar, High Energy Physics::Experiment, Nucleon, Nuclear Experiment
Abstract

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p \to \phi p$, $\gamma d \to \phi p n$ and $\gamma d \to \phi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma}$=1.6-2.4 GeV was used for the production of $\phi$ mesons. The natural-parity Pomeron exchange processes remains dominant nearthreshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from nucleons but is greatly reduced in the coherent production from deuterons. There is no strong $E_{\gamma}$-dependence, but some dependence on momentum-transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed., Comment: 25 pages, 14 figures

Published
2010
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2. Backward-angleηphotoproduction from protons atEγ=1.6–2.4 GeV

Author

Masato Yoshimura, Hidetoshi Akimune, C. W. Wang, Y. Ohashi, S. Hasegawa, M. Niiyama, Yorihito Sugaya, Tomoaki Hotta, Takahiro Iwata, T. Ooba, Y. Asano, T. Matsuda, Norihito Muramatsu, Hiroyuki Toyokawa, D. S. Ahn, A. Shimizu, J. K. Ahn, M. Miyabe, Y. Shiino, H. Kawai, Tetsuhiko Yorita, W. C. Chang, S. Fukui, Hajime Shimizu, Atsushi Sakaguchi, D. S. Oshuev, K. Yonehara, Tsutomu Mibe, T. Matsumura, S. C. Wang, M. Yosoi, H. Ejiri, Takatsugu Ishikawa, A. Wakai, R. G. T. Zegers, Y. Toi, Koichi Kino, N. Kumagai, H. Fujimura, P. M. Shagin, H. Kohri, M. Fujiwara, Takashi Nakano, K. Hicks, Masaharu Nomachi, Haruo Ohkuma, Chary Rangacharyulu, K. Imai, Y. Kato, S. Daté, and M. Sumihama

Subjects
Physics, Strongly coupled, Nuclear and High Energy Physics, Particle physics, Meson production, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Resonance (particle physics), Omega, Baryon, Nuclear physics, N channel, High Energy Physics::Experiment, Total energy, Nuclear Experiment
Abstract

Differential cross sections for {eta} photoproduction from protons have been measured at E{sub {gamma}}=1.6-2.4 GeV in the backward direction. A bump structure has been observed above 2.0 GeV in the total energy. No such bump is observed in {eta}{sup '},{omega}, and {pi}{sup 0} photoproductions. It is inferred that this unique structure in {eta} photoproduction is due to a baryon resonance with a large ss component that is strongly coupled to the {eta}N channel.

Published
2009
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3. Evidence for theΘ+in theγd→K+K−pnreaction by detectingK+K−pairs

Author

Y. Asano, S. C. Wang, A. Wakai, Y. Ohashi, P. M. Shagin, H. Kohri, Masato Yoshimura, T. Ooba, T. Matsumura, D. S. Oshuev, Tsutomu Mibe, M. Miyabe, M. Sumihama, H. Ejiri, Takashi Nakano, Y. Shiino, S. Fukui, Hidetoshi Akimune, M. Fujiwara, Masaharu Nomachi, N. Kumagai, D. S. Ahn, M. Niiyama, K. Horie, Tomoaki Hotta, Takahiro Iwata, K. Kino, Hiroyuki Toyokawa, Y. Kato, M. Yosoi, Chary Rangacharyulu, Y. Miyachi, K. Hicks, T. Matsuda, S. Daté, Haruo Ohkuma, Z. Y. Kim, S. Makino, H. Hasegawa, N. Matsuoka, Yorihito Sugaya, K. Imai, Norihito Muramatsu, H. Fujimura, C. W. Wang, H. Kawai, K. Yonehara, A. Shimizu, Atsushi Sakaguchi, Hajime Shimizu, Takatsugu Ishikawa, R. G. T. Zegers, Y. Toi, J. K. Ahn, W. C. Chang, and Tetsuhiko Yorita

Subjects
Scattering cross-section, Physics, Nuclear and High Energy Physics, Crystallography, Angular range, Mass distribution, Deuterium, Hyperon, High Energy Physics::Experiment, Invariant mass, Photon energy, Atomic physics
Abstract

The {gamma}d{yields}K{sup +}K{sup -}pn reaction has been studied to search for the evidence of the {theta}{sup +} by detecting K{sup +}K{sup -} pairs at forward angles. The Fermi-motion-corrected nK{sup +} invariant mass distribution shows a narrow peak at 1.524{+-}0.002+0.003 GeV/c{sup 2}. The statistical significance of the peak calculated from a shape analysis is 5.1 {sigma}, and the differential cross section for the {gamma}n{yields}K{sup -}{theta}{sup +} reaction is estimated to be 12{+-}2 nb/sr in the photon energy range from 2.0 to 2.4 GeV in the LEPS angular range by assuming the isotropic production of the {theta}{sup +} in the {gamma}n center-of-mass system. The obtained results support the existence of the {theta}{sup +}.

Published
2009
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4. Measurement of theγ→p→K+Λreaction at backward angles

Author

M. Niiyama, A. Shimizu, Masato Yoshimura, M. Morita, K. Yonehara, H. Ejiri, Sho Ozaki, N. Matsuoka, Hajime Shimizu, Atsushi Sakaguchi, J. K. Ahn, H. Kawai, Takashi Nakano, T. Matsuda, Y. Asano, Y. Ohashi, Masaharu Nomachi, Atsushi Hosaka, T. Ooba, S. Daté, Hidetoshi Akimune, S. Hasegawa, W. C. Chang, N. Kumagai, K. Kino, D. S. Oshuev, B. Juliá-Díaz, Z. Y. Kim, T.-S. H. Lee, S. Makino, Y. Shiino, M. Fujiwara, Tsutomu Mibe, C. W. Wang, Yorihito Sugaya, H. Kohri, T. Sasaki, R. G. T. Zegers, M. Sumihama, Y. Toi, M. Miyabe, D. S. Ahn, S. Fukui, Tomoaki Hotta, Takahiro Iwata, T. Matsumura, Norihito Muramatsu, Y. Miyachi, K. Imai, K. Hicks, Haruo Ohkuma, M. Yosoi, Tetsuhiko Yorita, Y. Kato, T. Ishikawa, S. C. Wang, H. Fujimura, A. Wakai, P. M. Shagin, Hiroyuki Toyokawa, and Chary Rangacharyulu

Subjects
Physics, Nuclear and High Energy Physics, Photon, 010308 nuclear & particles physics, media_common.quotation_subject, Hadron, Lambda baryon, Lambda, 01 natural sciences, Asymmetry, Particle identification, Particle decay, Pion, 0103 physical sciences, High Energy Physics::Experiment, Atomic physics, Nuclear Experiment, 010306 general physics, media_common
Abstract

Cross sections for the {gamma}p{yields}K{sup +}{lambda} reaction were measured at backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV. In addition, the beam asymmetry for this reaction was measured for the first time at backward angles. The {lambda} was detected at forward angles in the LEPS spectrometer via its decay to p{pi}{sup -} and the K{sup +} was inferred using the technique of missing mass. These measurements, corresponding to kaons at far backward angles in the center-of-mass frame, complement similar CLAS data at other angles. Comparison with theoretical models shows that the reactions in these kinematics provide further opportunities to investigate the reaction mechanisms of hadron dynamics.

Published
2007
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