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Study of Weak Hyperon Nucleon Interaction by means of Decay Particle Spectroscopy

衰变粒子光谱研究弱超子核相互作用

基本信息

批准号：
08239205
负责人：
KISHIMOTO Tadafumi
金额：
$ 35.33万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

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 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 focused our attention to the phenomena which originate short range interaction. Following subjects were studied in this research.(1) 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.(2) 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ィイD1-ィエD1, πィイD1-ィエD1) using kaon beam provided 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.(3) Production of strangeness by weak interaction.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 designing 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不能很好地理解，特别是因为我们无法描述基于已知原理的夸克禁闭。除了在模型中必须考虑强子大小的短距离情况外，核子-核子相互作用可以用介子交换理论很好地描述。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使得可以清楚地确定自由度的存在。对于许多能很好地描述神经网络相互作用的模型，该模型的SU(3)扩展应该是最好的检验依据。在本研究中，我们将注意力集中在源于短程相互作用的现象上。主要研究内容如下：(1)超核弱非介子衰变中的宇称破坏。弱非介子衰变N，Λ→，NN具有很大的动量转移，使得短距离相互作用至关重要。我们证明了极化Λ超核和弱非介子衰变的产生具有不对称的角分布，相应的宇称破坏。宇称破坏的大小与介子交换模型不一致。(2)测量了ィイD313(/)ΛィエD3C的自旋-轨道相互作用。Λ超核的自旋轨道分裂是已知的，尽管实验没有给出确定值。我们用北京天文台AGS提供的Kaon束产生了ィイD313(/)ΛィエD3C(KィイD_1-ィエD_1，πィイD_1-ィエD_1)，并通过探测γ射线测量了分裂。发现分裂比核子的分裂小20-40倍。(3)弱相互作用产生奇异性。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)。这是一个通过弱相互作用产生陌生感的过程。它从未受到过挑战。通过对探测器的精心设计，我们发现实验是可行的。