| Project/Area Number |
14340075
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Osaka University |
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Principal Investigator |
NAKANO Takashi Osaka University, Research Center for Nuclear Physics, Professor, 核物理研究センター, 教授 (80212091)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA Mamoru Osaka University, Associate Professor, 核物理研究センター, 助教授 (00030031)
HOTTA Tomoaki Osaka University, Research Associate, 核物理研究センター, 助手 (30332745)
菅谷 頼仁 大阪大学, 理学研究科, 助手 (80324747)
TOKI Hiroshi Osaka University, Professor, 核物理研究センター, 教授 (70163962)
HOSAKA Atsushi Osaka University, Associate Professor, 核物理研究センター, 助教授 (10259872)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥13,800,000 (Direct Cost: ¥13,800,000)
Fiscal Year 2003: ¥7,100,000 (Direct Cost: ¥7,100,000)
Fiscal Year 2002: ¥6,700,000 (Direct Cost: ¥6,700,000)
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| Keywords | Phi-meson / Pomeron / Laser-Electron Photon / Theta particle / 光生成 / グルーオン / グルーボール |
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| Research Abstract |
Since a $phi$ meson is almost pure s s_bar state, diffractive photo-production for a Ф meson off a proton in a wide energy range is well described as a pomeron-exchange (multi gluon-exchange) process in the framework of the Regge theory and of the Vector Dominance Model ; a high energy photon converts into a Ф meson and then it is scattered from a proton by an exchange of the pomeron while the meson-exchange is suppressed by the OZI rule. However, at low energies other contributions arising from meson (π, η)-exchange, a scaler (0^<++>glueball)-exchange, and ss_bar knock-out are possible. These contributions fall off rapidly as the incident photon energy increases, and can be studied only in the low energy region near the production threshold. Linearly polarized photons are an ideal probe to decompose these contributions. For natural-parity exchange such as pomeron and 0^<++>glueball exchanges, the decay plane of $K^+K^-$ is concentrated in the photon polarization vector. For unnatural-parity exchange processes like π and ηexchange processes, it is perpendicular to the polarization vector. A preliminary analysis of the KK decay asymmetry for Φphoto-productions in the forward angles showed the natural-parity exchange contributions are still dominant. The cross-section shows a bump structure near 2 GeV which cannot be explained by Pomeron exchange contribution only. Thus we conclude there must be additional natural-parity exchange contribution, which may be attributed to a new Regge trajectory associated with 0^<++> glueball. As a bi-product of this study, we found evidence for a narrow S=+1 baryon resonance in photo-production from a neutron, which may be interpreted as a Pentaquark state Θ^+.
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