Phi-meson photo-production to study multi-gluon exchange process

菲介子照片制作研究多胶子交换过程

• 批准号: 14340075
• 负责人: NAKANO Takashi
• 金额: $ 8.83万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340075/
• 关键词: Phi-meson; Pomeron; Laser-Electron Photon; Theta particle; 光生成; グルーオン; グルーボール

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^+.

由于 $phi$ 介子几乎是纯 s s_bar 态，因此在宽能量范围内质子的 Ф 介子的衍射光产生被很好地描述为 Regge 框架中的波默子交换（多胶子交换）过程理论和矢量优势模型；高能光子转换为 Ф 介子，然后通过波默子的交换从质子中散射出来，而介子交换是然而，在低能量下，介子 (π, η) 交换、缩放器 (0^<++>glueball) 交换和 ss_bar 敲除产生的其他贡献可能会下降。随着入射光子能量的增加而迅速增加，并且只能在接近产生阈值的低能量区域进行研究，线性偏振光子是分解这些贡献的理想探针，例如波默子和。 0^<++>胶球交换，$K^+K^-$ 的衰变平面集中在光子偏振矢量中，对于 π 和 η 交换过程等非自然宇称交换过程，它垂直于偏振矢量 A。对前角 Φ 光产生的 KK 衰变不对称性的初步分析表明，自然宇称交换贡献仍然占主导地位，横截面显示出 2 GeV 附近的凸块结构，无法解释。因此，我们得出结论，一定存在额外的自然平价交换贡献，这可能归因于与 0^<++> 胶球相关的新 Regge 轨迹。对于中子光产生中的窄 S=+1 重子共振，这可以解释为五夸克态 θ^+。

项目成果

Evidence for Narrow S=+1 Baryon Resonance in Photo-production from Neutron

中子照片制作中窄 S= 1 重子共振的证据

• 发表时间: 2003
• 期刊: Physical Review Letters 91
• 作者: T.Nakano;et al.
• 通讯作者: et al.