There are some discrepancies in the low energy data on the photoabsorption cross section of $^4$He. We calculate the cross section with realistic nuclear forces and explicitly correlated Gaussian functions. Final state interactions and two- and three-body decay channels are taken into account. The cross section is evaluated in two methods: With the complex scaling method the total absorption cross section is obtained up to the rest energy of a pion, and with the microscopic $R$-matrix method both cross sections $^4$He($γ, p$)$^3$H and $^4$He($γ, n$)$^3$He are calculated below 40\,MeV. Both methods give virtually the same result. The cross section rises sharply from the $^3$H+$p$ threshold, reaching a giant resonance peak at 26--27\,MeV. Our calculation reproduces almost all the data above 30\,MeV. We stress the importance of $^3$H+$p$ and $^3$He+$n$ cluster configurations on the cross section as well as the effect of the one-pion exchange potential on the photonuclear sum rule.
在半经典相空间模型的框架下，计算了300 MeV ~ 1 GeV能量范围内原子核的总光吸收截面.除了介质的修改，如费米运动和泡利阻塞，我们专注于碰撞所涉及的共振加宽。共振贡献的基本截面固定的π介子光生的分波振幅。计算碰撞增宽所需的$N \, R \to N \, N$的截面是通过拟合到$N \, N \to N \, N \, π$截面的细致平衡获得的。我们表明，一个合理的碰撞加宽是无法解释的实验观察到的消失的$D_{13}(1520)$共振的光吸收截面上的核。
Finite-spectrum Lorentz integral transform calculation of the $^{4}$He photoabsorption cross section in the no-core shell model
College of Physics and Engineering, Henan University of Science and Technology（河南科技大学物理与工程学院）；State Key Laboratory of Heavy Ion Science and Technology, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所重离子科学和技术重点实验室）；Department of Physics and Astronomy, Iowa State University（爱荷华州立大学物理与天文系）；CAS Key Laboratory of High Precision Nuclear Spectroscopy, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所高精度核谱学重点实验室）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）
Li 7的总光吸收截面在显微镜下计算。作为核子-核子相互作用，采用了具有S波和P波力的半现实中心AV 4 '势。采用洛伦兹积分变换（LIT）方法，充分考虑了末态7核子系统的相互作用。对于LIT的计算，我们使用超球谐函数（HH）的扩展结合HH有效相互作用（EIHH）的方法。详细讨论了LIT展开式的收敛性。计算的截面与现有的实验数据吻合得很好，这些数据涵盖了从阈值到100 MeV的能量范围。
The inclusive reaction d(γ,π)NN in the first resonance region
在第一共振区研究了氘核光生单π介子的包容性。计算是基于使用图解法。极点图和单回路图与NN再散射在最终状态考虑。核子光生π介子的基本算符取在壳层形式，用SAID和MAID多极分析计算。我们的预测总的和微分截面显示出良好的协议与现有的实验数据。通过对反应$gamma d\toπ^0 d and $ γd \to np$的计算，我们预测了氘的总光吸收截面。我们发现我们的结果高估了Δ峰中心（\sim 320 MeV）的实验数据约10%。
