Molecular Structures of Strangeness Light-nuclei and their Response Spectra

1.超核奇异性核平均场的Hartree-Fock(HF)和密度相关的Hartree-Fock(DDHF)计算是基于有限范围内的ΝΝ和ΛΝ有效相互作用进行的。我们讨论了^&lt；17&gt；_ΛO和^5_ΛHe的结构以及Λ超子的加入引起的核心极化效应。我们强调，在DDHF中，核心极化(重排)能ΔE_N对于(Os)_Λ为~2 MeV，对于(Op)_Λ为~1 MeV。核子的总能量E_N减小的原因是核子s.p。能量e_α随着Λ的加入而变深。ΔE_N的能量取决于ΝΝ有效相互作用的性质和ΛΝ有效相互作用重现实验数据的能力。2.奇异核的产生及其响应谱我们提出了一个关于DWIA内核反应的“最佳费米平均近似”。我们用它计算了^&lt；12&gt；C(π^+，K^+)反应的准自由谱，并与实验数据进行了比较。结果表明，由于能量依赖关系源于最优费米平均t-矩阵的性质，所以计算的光谱与数据符合得很好。然后我们把它的(π^-，K^+)谱推广到^&lt；12&gt；C和^&lt；28&gt；Si靶上，从数据中提取Σ^--核势的性质。我们发现^&lt；28&gt；Si的Σ^--核势具有V^0_Σ[相似或相等]+20~+40 MeV的排斥力，而Σ-Saxon型势有-10~-30 MeV的相当大的吸收，并且一个再现Σ^-原子X射线数据的π^--核势将再现(π^-，K^+)谱。此外，我们利用耦合的(3Λ)+(3Ν-Σ)模型，通过(Stoped K^-，π^-)反应中的Ν-Λ组分，预测了^4_Ν-ΣHe基态的占有率约为20%。

1.Mean-field calculations for strangeness-nucleiHartree-Fock (HF) and Density-dependent Hartree-Fock (DDHF) calculations for hypernuclei are performed on the basis of ΝΝ and ΛΝ effective interactions with a finite-range. We discuss structures of ^<17>_ΛO and ^5_ΛHe and core-polarization effects arising from the addition of the Λ-hyperon. We stress that the core-polarization (rearrangement) energy ΔE_N is 〜2 MeV for (Os)_Λ and 〜1 MeV for (Op)_Λ in the DDHF. The reason why the total energy E_N of the core is reduced is because the nucleon s.p. energy e_α becomes deeper by the addition of the Λ. Energies of ΔE_N depend on the nature of the ΝΝ effective interaction and the capacity of the ΛΝ effective interaction to reproduce the experimental data.2.Production of strangeness-nuclei and their response spectraWe propose an "optimal Fermi-averaging approximation" to nuclear reactions within the DWIA. We apply it to calculate A quasi-free spectra from ^<12>C(π^+,K^+) reactions, and compare them with experimental data. The results show that the calculated spectra are in excellent agreements with the data, because the energy-dependence originates from the nature of the optimal Fermi-averaging t-matrix. Then we extend it (π^-,K^+) spectra on ^<12>C and ^<28>Si targets in order to extract properties of Σ^--nucleus potential from the data. We find that the Σ^--nucleus potential for ^<28>Si has a repulsion of V^0_Σ【similar or equal】 +20 〜 +40 MeV, and a sizable absorption of -10 〜 -30 MeV for a Woods-Saxon type potential, and that a Σ^--nucleus potential reproducing the Σ^-atomic x-ray data, would reproduce the (π^-,K^+) spectra. Moreover, we predict that the ^4_ΛHe ground state is populated by about 20% via Σ components in (stopped K^-,π^-) reactions, using a coupled (3Ν-Λ)+(3Ν-Σ) models.