A Test of QCD at Low Energy by measuring a Lifetime of Di-mesonic Atoms

通过测量双介子原子寿命来测试低能 QCD

• 批准号: 12440069
• 负责人: OKADA Kenji
• 金额: $ 9.28万
• 依托单位: Kyoto Sangyo University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440069/
• 关键词: QCD; Hadronic Atom; Scintillating fiber; Chiral Perturbation; Topological Trigger; ππ scattering length; Atom; PSPM; 中間子原子; シンチレーティングファイバ; 位置検出型光電子増倍管; ハイドロニック原子; DIRAC; トポロジロルートリガー

The DIRAC experiment (PS2 12) aims to measure the lifetime of π+π-atoms using 20GeV proton beam provided by the CERN PS. The precise measurement of the lifetime enables to determine a s-wave pion-pion scattering length in a model independent way. The ππ scattering length have been calculated by means of Chiral perturbation theory with a precision of 5% at the starting stage of the DIRAC experiment. Now the precision of the calculation is better than 2.5%. The results are based on the assumption of a spontaneous chiral symmetry breaking due to a strong quark condensation. Therefore, a precise comparison of the theoretical value with the experimental one provides an opportunity to verify the current understanding of chiral symmetry breaking in QCD and to check the magnitude of the quark condensation.Japan group has developed a topological trigger device consisting of scifi-hodos, a peak sensing circuit and a trigger logic circuit. They can select out on line a real π+π-pair due to π+π-atom breaking-up from a huge amount of background events.The expected statistical accuracy of |aO-a2| scattering length obtained in the DIRAC experiment will be about 6% at the present stage. Although this value was a goal at the beginning, now it is still 3 times larger than the corresponding theoretical accuracy. An extension of this experiment applied for the LOI of the J-PARC is adopted

狄拉克实验(PS212)的目的是利用欧洲核子研究中心提供的20GeV质子束测量π+π原子的寿命。寿命的精确测量使我们能够以一种与模型无关的方式确定S波的介子-介子散射长度。在狄拉克实验的初始阶段，用手征微扰理论计算了ππ散射长度，精度为5%。目前计算精度优于2.5%。这些结果是基于强夸克凝聚导致手征对称性自发破缺的假设。因此，将理论值与实验值进行精确的比较，为验证目前对QCD手征对称性破缺的理解和检验夸克凝聚的大小提供了机会。日本研究小组开发了一种由Science-Hodos、峰值传感电路和触发逻辑电路组成的拓扑触发装置。他们可以从大量的背景事件中在线挑选出一个真实的π+π对，在现阶段，π+π实验中获得的|aO-a2|散射长度的预期统计精度将达到6%左右。虽然这个值在开始时是一个目标，但现在它仍然比相应的理论精度大3倍。本实验的扩展被应用于J-PARC的LOI

项目成果

The DIRAC collaboration: "DIRAC : A High Resolution Spectrometer for Pionium Detection."Nucl.Inst.Meth.in Physics Research A. A515. 467-496 (2003)

DIRAC 合作：“DIRAC：用于锍检测的高分辨率光谱仪。”Nucl.Inst.Meth.in 物理研究 A. A515。

M.Kobayashi: "Silicon strip detectors as a real-time, fast, medium-segmented hodoscope."Nucl.Inst.Meth.in Physics Research A. A487. 353-364 (2002)

M.Kobayashi：“硅条探测器作为实时、快速、中分段的视距镜。”Nucl.Inst.Meth.in 物理研究 A. A487。

P.Gianotti: "Test of chiral perturbation theory with DIRAC at CERN"Acta Phys.Polon.B. B31. 2571-2579 (2000)

P.Gianotti：“在 CERN 使用 DIRAC 测试手性微扰理论”Acta Phys.Polon.B。

M.Kobayashi et al.: "Silicon strip detector as a real-time, fast, medium-segmented hodoscope"Nucl. Inst. And Meth. in Phys. Res.. A487. 353-364 (2002)

M.Kobayashi 等人：“硅条检测器作为实时、快速、中等分段的视距仪”Nucl。

L.Afanasyev et al.: "The multilevel trigger system of the DIRAC experiment"Nucl. Inst. and Meth. in Phys. Res.. A491. 376-389 (2002)

L.Afanasyev 等：“DIRAC 实验的多级触发系统”Nucl。