Study of reaction mechanism of Theta+photo-production

Theta光产生反应机理研究

• 批准号: 16204017
• 负责人: NAKANO Takashi
• 金额: $ 32.2万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16204017/
• 关键词: Theta+; Laser-Electron Photon; Pentaquark; レーザー電子光ビーム; タイムプロジェクションチェンバー; Deep-UV発振レーザー

The Theta+ particle is a 5-quark particle (pentaquark) for which the evidence was first reported by LEPS/Spring-8 collaboration by analyzing an experimental data taken with a Laser-Electron-Photon beam on a nuclear target.This study aims to confirm the existence of the Theta+ by using a high intensity beam with higher statistics. And if the its existence was confirmed, the structure of the pentaquark such as spin and parity would be investigated. In this study, first, the beam intensity was doubled by replacing an Ar laser by two solid-state lasers with the output power of 8W. The LEP beam intensity reached at 2 M Hz by inserting two laser beams into the electron ring simultaneously. The laser optics has been modified to avoid the beam loss due to distortion of the optics elements by heat. The tagger system has been also modified so that dead-time due to the high rate becomes small. The efficiency and the resolution of the tagger was studied and turned out to be good enough for the Theta+ study. In 2006-2007, the major physics run has been carried out and the data with 3 more statistics than the previous run was obtained. The detailed analysis of the previous run was also carried out, and the Theta+ signal with a 5 standard sigma significance was observed by correcting Fermi-motion effect in the missing mass calculation. A blind analysis will be carried out for the new data set to confirm the signal.Hyperon and meson photo-production reactions were also studied by analyzing the same data. Results were published on journals.

Theta+粒子是一种5夸克粒子(五夸克)，这一证据是由LEPS/Spring-8合作通过分析激光-电子-光子束在核目标上拍摄的实验数据首次报道的。本研究旨在通过使用具有更高统计量的高能强束来证实Theta+粒子的存在。如果证实了它的存在，将研究五夸克的结构，如自旋和宇称。在这项研究中，首先，用两个输出功率为8W的固体激光器取代一个Ar激光器，使光束强度加倍。通过在电子环中同时插入两束激光，获得了2 M Hz的LEP光束强度。对激光光学元件进行了改装，避免了由于光学元件受热变形而造成的光束损失。标记机系统也进行了修改，因此由于高比率而导致的停滞时间变得更小。研究了标记器的效率和分辨率，结果证明足够好，可以用于Theta+研究。在2006-2007年进行了重大物理运行，获得了比前一次运行多3个统计量的数据。对前一次运行也进行了详细的分析，通过修正丢失质量计算中的费米运动效应，观察到了具有5标准西格玛意义的Theta+信号。为了确认这一信号，将对新的数据集进行盲分析。通过分析相同的数据，还研究了超子和介子的光生反应。研究结果发表在期刊上。

项目成果

The γ P→K^+∧ and γ P→K^+ Σ^0 reactions at forward angles with photon energies from 1.5 GeV to 2.4 GeV

γ P→K^+∧ 和 γ P→K^+ Σ^0 反应在正向角，光子能量为 1.5 GeV 至 2.4 GeV

• 发表时间: 2006
• 期刊: Phys.Rev.C 73
• 作者: M.Sumihama;J.K.Ahn;H.Akimune;Y.Asano;T.Nakano;その他48名
• 通讯作者: その他48名

Evidence for + photo-production at LEPS

LEPS 的照片制作证据

• 发表时间: 2007
• 作者: Koji Shimomura;Kazuo Nishimura;S.Miyoki et al.;小野薫;中野 貴志
• 通讯作者: 中野 貴志

Dfferential cross section and photon beam asymmetry for the γn→K^+ Σ^- reaction at Eγ=1.5 GeV-2.4 Ge V

Eγ=1.5 GeV-2.4 Ge V 时 γn→K^+ Σ^- 反应的微分截面和光子束不对称性

• 发表时间: 2006
• 期刊: Phys. Rev. Lett. 97
• 作者: H. Kohri;D.S. Ahn;J.K. Ahn;H. Akimune;T. Nakano;et. al.
• 通讯作者: et. al.

Evidence forΘ^+ photo-production at LEPS

LEPS θ^+ 照片制作的证据

• 发表时间: 2007
• 作者: D.Fathi;L.Elisabeth;Y.Nishiura;Takashi Nakano
• 通讯作者: Takashi Nakano

Differential cross section and photon beam asymmetry for the γn→K^+Σ reaction at Eγ=1.5 GeV-2.4 GeV

Eγ=1.5 GeV-2.4 GeV γn→K^+Σ 反应的微分截面和光子束不对称性

• 发表时间: 2006
• 期刊: Phys.Rev.Lett. 97
• 作者: H.Kohri;D.S.Ahn;J.K.Ahn;H.Akimune;T.Nakano;その;他52名
• 通讯作者: 他52名