Spin correlation in pion-nucleus reaetions

我取得了以下成果：1.我首次对临界值附近的(p，pi^-)反应进行了有限范围的DWBA计算。与实验数据吻合较好。我还预测了高能区的(p，pi^-)谱。由于介子的波长较长，在低能区的介子-核光学势中的参数很难唯一确定。通过对深度束缚离子原子中四极超精细成分的研究，指出了确定这些参数的可能性。通常在动量空间中处理波动方程，如薛定谔方程或狄拉克方程。在这种情况下，长程库仑力造成了数值困难。对于动量空间中的库仑力，我们提出了一种简单而又相当精确的数值方法。根据唯象的准氘核模型，分析了~3He和~4He的光解截面。我们的模型成功地描述了最近实验结果的总体特征。我们发展了一种新的算法，使我们能够处理量子多体系统的激发态性质，基于辅助场蒙特卡罗方法。我们已将该方法应用于一些精确可解的模型，并检验了该方法在实际案例中的适用性。

I have obtained the following results.1. I have carried out the finite-range DWBA calculation of the pion energy spectrum for (p, pi^-) reactions near threshold for the first time. Good agreement with the experimental data is obtained. I have also made predictions of the (p, pi^-) spectrum in higher energy region.2. The parameters in the pion-nucleus optical potential in low-energy region is known to be difficult to determine uniquely due to the long wavelength of the pions. I have pointed out the possibility of fixing these parameters from the study of the quadrupole hyperfine component in deeply bound pionic atoms.3. The wave equations such as Schrodinger or Dirac equations are often treated in the momentum space. In this case, the long-range Coulomb force causes numerical difficulty. We proposed a simple and quite accurate numerical method to treat the Coulomb force in momentum space.4. We have analyzed the photo-disintegration cross sections in ^3He and ^4He according to the phenomenological quasi-deuteron model. Our model successfully decribe the overall features of the recent experimental results.5. We have developed a novel algorithm which enables us to treat the excited-state properties of the quantum many-body system based on the auxiliary-field Monte Carlo method. We have applied this method to some exactly solvably models and have examined the applicability of this method to realistic cases.