Speaker: Calvin Johnson (San Diego State University)

Microscopic modeling of nuclear level densities using spectral distribution theory

Nuclear level densities are important inputs into modeling statistical neutron capture rates at low-to-medium energies. Level densities are, however, difficult to come by, and often are the most uncertain component of Hauser-Feshbach calculations. We use spectral distribution theory (also known as statistical spectroscopy) to model the level densities. Starting with well-validated shell-model interactions, we compute partitioned moments of the many-body nuclear Hamiltonian, and model the density of states as a sum of binomials with their first, second, and third moments fixed. Where we can compare with other results such as direct diagonalization we get very good results. Finally, we can also compute energy-dependent expectation values of other operators, such as angular momentum and center-of-mass motion, which allows us to usefully separate out densities with different quantum numbers. This in particular is unique among approaches to level densities.