THEORETICAL STUDY OF NUCLEI WITH STRANGENESS

该项目由五个主要主题组成，取得了以下成果。(1)对轻超核能谱进行了微观三体和四体团簇模型计算：证实了Λ参与下核芯的收缩。分析了自旋-自旋和自旋-轨道Λ-N相互作用的作用。结果表明，在质量为4的Σ超核低激发态中掺入Λ组分，具有反映YN相互作用性质的特征作用。DW IA计算成功地解释了飞行中和停止(K-，π)反应光谱。(2)从理论上对双Λ超核的产生率进行了估算。在典型的S=-2系统中也研究了超子混合的影响。(3)值得注意的是，已经提出了几个新的YN和YY相互作用的介子理论模型，并在超核结构中进行了验证。此外，夸克模型还给出了重子-重子相互作用的几种版本。夸克模型已扩展到计算核物质中氢粒子的相互作用。(4)为了解释超核弱衰变(寿命)的新实验数据，除了OPE过程外，还对关联的两π交换过程和直接夸克过程进行了评价。人们发现，它们都有一定的有利作用，但并不总是充分的。(5)在研究项目中应用和发展了重要的计算方法：典型的量子分子动力学(QMD)方法、高斯基耦合重排通道方法和复标度方法。

The project consists of five major subjects which lead to the following achievements. (1) The microscopic three- and four-body cluster model calculations have been carried out for spectroscopy of light hypernuclei : The shrinkage of the nuclear core under the effect of Λ participation has been confirmed. The role of spin-spin and spin-orbit ΛN interactions has been analysed. It has been revealed that the admixture of Σ component into the mass-4 Λ hypernuclear low-lying states has a characteristic role reflecting the properties of YN interaction adopted. The in-flight and stopped (K-, π) reaction spectra are successfully explained by the DWIA calculation. (2) Several theoretical attempts have been presented to evaluate the production rates of double-Λ hypernuclei. The effect of hyperon mixing has been also investigated in typical S = -2 systems. (3) It is remarkable that several meson theoretical models of new YN and YY interactions have been presented to be tested in the hypernuclear structure. Moreover the quark models also presented several versions of the baryon-baryon interactions. The quark model has been extended to evaluate the interaction of the H particles in nuclear matter. (4) In order to explain new experimental data of hypernuclear weak decays (lifetimes), the correlated two-pion exchange process and the direct (quark process were evaluated in addition to the OPE process. It has been found that they have both certain favorable effects but are not always sufficient. (5) The important calculational methods have been applied and developed in the research project : the typical examples are the quantum molecular dynamics (QMD) approach, the Gaussian basis coupled-rearrangement channel method and the complex scaling method.