Theory developments for obtaining compound-nuclear cross sections from indirect data

Low-energy neutron-induced reactions play an important role in nuclear physics and other fields that seek to understand physical processes in which neutrons react with their environment. Many required cross sections are unknown and extremely difficult to determine experimentally, as their measurement involves colliding neutrons with short-lived or highly-radioactive targets. The presence of isomers in the target or intermediate nuclei involved further complicates the situation. The surrogate reaction method [1], an indirect approach, has been demonstrated to provide meaningful constraints for cross sections of (n,g), (n,n'), and (n,2n) reactions [2-6]. Results from recent extensions of the theory that enable a broader application of this indirect approach, as well as better uncertainty quantification, will be presented.

[1] J. E. Escher et al, Rev. Mod. Phys. 84, 353 (2012)

[2] J. E. Escher et al, PRL 121, 052501 (2018)

[3] A. Ratkiewicz et al, PRL 122, 052502 (2019)

[4] R. Perez Sanchez et al, PRL 125, 122502 (2020)

[5] J. E. Escher, Techn. Rep., LLNL-TR-839279 (LLNL, 2022)

[6] J. E. Escher and A. Ratkiewicz, Techn. Rep., LLNL-MI-865936 (LLNL, 2024)