Study of Short Range Hyperon Necleon Interaction

短程超子核相互作用研究

• 批准号: 10044086
• 负责人: KISHIMOTO Tadafumi
• 金额: $ 3.46万
• 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: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10044086/
• 关键词: Hypernuclei; Strangeness; Weak nonmeonic decay; Spin-orbit interaction; Baryon-Baryon Interaction; Short Range correlation; Quark degeree of freedom; バリオン間相互作用; ハイペロン

It is well known that hadrons (Baryons and mesons) are made up of quarks and gluons by the strong interaction. The interaction among hadrons is not well understood especially due to our inability to describe the quark confinement beased on a known principle. The nucleon interaction is well described by meson exchange theory except at short distances where size of hadrons has to be taken into account in the model. Quark and gluon degrees of freedom have to be present though flexibility of the meson change model forbits to pin down clearly the existence of the freedom. The SU (3) extention of the model should be the best testing gound for many models that describe well the NN interaction. In the present research we forcused our attention to the phenomena which originate short range interaction. Following subjects were studied in this research.(1) Spin-orbit interaction ofィイD313(/)ΛィエD3C was measured.Spin-orbit splitting of Λ hypernuclei is known to be small though no definite value has been given by experiments. We produced ィイD313(/)ΛィエD3C by the (K-, π-) using kaon beam provied by the AGS at BNL and measured the splitting by detecting γ rays. The splitting was found to be 20-40 times smaller than that of nucleons.(2) Parity violation in the weak nonmesonic decay of hypernuclei.Weak nonmesonic decay NΛ→NN has a large momentum transfer that make interaction at short distance vital. We demonstrated production of polarized Λ hypernuclei and weak nonmesonic decay has asymmetric angular distribution corresponding parity violation. The magnitude of the parity violation is found to be inconsistent with meson exchange model. As for the further study we are preparing an experiment to measure the inverse reaction (pn→pΛ) of the weak nonmesonic decay. It is a process to produce strangeness by weak interaction. It has never been challenged. We found that the experiment is feasible by carefully desining the detector.

众所周知，强子（重子和介子）是由夸克和胶子通过强相互作用组成的。强子之间的相互作用还没有得到很好的理解，特别是由于我们无法描述夸克禁闭基于一个已知的原则。介子交换理论很好地描述了核子间的相互作用，但在短距离时，模型中必须考虑强子的大小。夸克和胶子的自由度必须存在，尽管介子变化模型的灵活性无法明确地确定自由度的存在。该模型的SU（3）扩展应该是许多能很好地描述神经网络相互作用的模型的最佳检验基础。在目前的研究中，我们把注意力集中在产生短程相互作用的现象上。本研究主要研究了以下几个问题。(1)测量了超核D313（/）Λ超核D3 C的自旋-轨道相互作用，发现Λ超核的自旋-轨道分裂很小，但实验没有给出确切的数值。我们利用BNL的AGS提供的K ~-离子束产生了D_313（/）Λ Λ Λ Λ D_3C，并通过探测γ射线测量了其分裂。发现分裂比核子的分裂小20-40倍。(2)超核弱非介子衰变中的宇称破缺弱非介子衰变NΛ→NN具有很大的动量转移，这使得近距离相互作用至关重要。我们证明了极化Λ超核的产生和弱非介子衰变具有不对称的角分布，对应于宇称破缺。发现宇称破坏的大小与介子交换模型不一致。至于进一步的研究，我们正在准备一个实验来测量弱非介子衰变的逆反应（pn→pΛ）。这是一个由弱相互作用产生奇异性的过程。它从未受到挑战。通过对探测器的仔细设计，我们发现实验是可行的。

项目成果

S. Ajimura, M. ishikawa, K. Ikeda, T. Kishimoto, A. Okusu, N. Shinkai, Y. Tanaka, H. Ejiri and T. Nakano, T. Nagae, K. Manabe, H. Noumi, M. Sekimoto, and T. Shibata, O. Hashimoto, K. Maeda, and T. Tak: "Asymmetry in Nonmesonic Weak Decay of Polarized 5ィイD

S. Ajimura、M. ishikawa、K. Ikeda、T. Kishimoto、A. Okusu、N. Shinkai、Y. Tanaka、H. Ejiri 和 T. Nakano、T. Nagae、K. Manabe、H. Noumi、M. Sekimoto、T. Shibata、O. Hashimoto、K. Maeda 和 T. Tak：“极化非介声弱衰变中的不对称性”

S. Ajimura, M. Ishikawa: "Polarization of ^5_ΛHe Produced by the (π^+, K^+) Reaction"Phys. Rev. Lett.. 80. 3471-3474 (1998)

S. Ajimura、M. Ishikawa：“(π^+, K^+) 反应产生的 ^5_ΛHe 的极化”Phys. Rev. Lett.. 80. 3471-3474 (1998)

I.G.Bearden: "High Energy Pb+Pb Collisions Viewed by Pion Interferometry" Physical Review C. 58. 1656-1665 (1998)

I.G.Bearden：“通过 Pion 干涉测量观察到的高能 Pb Pb 碰撞”物理评论 C. 58. 1656-1665 (1998)

S. Ajimura, M. Ishikawa: "Asymmetry in Nonmesonic Weak Decay of Polarized ^5_ΛHe Hypernuclens"Phys. Rev. Lett., in press.

S. Ajimura、M. Ishikawa：“极化 ^5_ΛHe 超核透镜的非介声弱衰变中的不对称性”Phys Rev. Lett.，出版中。

H. Nabetani, T. Ogaito, T, Sato, T. Kishimoto: "Spin observables in the pn → pΛ reaction"Phys. Rev.. C60. 017001-1-017001-4 (1999)

H. Nabetani、T. Ogaito、T、Sato、T. Kishimoto：“pn → pΛ 反应中的自旋观测值”Phys. Rev. 017001-1-017001-4 (1999)