2026/08/04 by P. Yin, H. T. Zhao, C. Y. Zhai +11
Physics and Astronomy · #nucl-ex #nucl-th
We develop and validate a finite-spectrum implementation of the Lorentz integral transform (LIT) within the ab initio no-core shell model (NCSM) for calculating the photoabsorption cross section of 4He. A large set of 1- eigenstates is explicitly calculated in the NCSM, and the LIT is constructed from their excitation energies and the corresponding E1 transition strengths. This finite-spectrum approach is complementary to conventional inhomogeneous-equation and Lanczos-based implementations of the LIT method for photoabsorption cross sections. Using the Daejeon16 interaction, we extract the photoabsorption cross section and examine its stability with respect to the model-space truncation, excitation-energy cutoff, and LIT parameters. The reliability of the finite-spectrum extraction is assessed by comparing the E1 polarizability and bremsstrahlung sum rule obtained from the discrete NCSM spectrum with the same quantities obtained by integrating the extracted cross section. The extracted cross section captures the principal features of the available 4He photonuclear data in the giant-dipole-resonance region and is consistent, in the low-energy rise and main-peak region, with earlier chiral-interaction NCSM-LIT results obtained from Lanczos-based evaluations, while the present calculation with the Daejeon16 interaction exhibits a more pronounced high-energy shoulder. The present work provides a controlled finite-spectrum NCSM-LIT route from explicitly calculated many-body eigenstates and transition strengths to photoabsorption cross sections.