Speaker
Description
The availability of reliable nuclear data with quantified uncertainties is essential for basic and applied science. The last decade has seen much progress in the development of theory tools that allow us to achieve more accurate evaluations for compound (statistical) nuclear reactions. Integrated nuclear structure and reaction descriptions provide the basis for achieving consistent evaluations across multiple isotopes and also enable indirect (surrogate) measurements of cross sections that are difficult to measure directly. This is particularly important for applications involving reactions with unstable nuclei, such as multi-physics simulations undertaken to understand stellar evolution and the synthesis of the elements.
I will discuss recent advances at the intersection of direct and compound-nuclear reactions. Progress made in describing direct reactions that populate doorway states has provided new insights into the formation of compound nuclei and enabled indirect measurements of compound-nuclear reactions. The reaction descriptions require the integration of nuclear-structure information that is not part of typical reaction calculations, as well as explicitly accounting for higher-order reaction processes. I will summarize the extensions of the theory and the experimental evidence that prompted them. The theory developments have enabled the successful extraction of neutron-capture cross sections from measurements of transfer reactions with stable beams [1,2]. I will discuss the use of inelastic scattering as another indirect (surrogate) mechanism, the feasibility of determining (n,2n) and other desired cross sections, and possible experiments at radioactive-beam facilities.
[1] Escher et al., PRL 121, 052501 (2018)
[2] Ratkiewicz et al., PRL 122, 052502 (2019)
*This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Support from the Laboratory Directed Research and Development Program at LLNL, Projects No. 19-ERD-017, 20-ERD-030, 21-LW-032, 22-LW-029, is acknowledged.