Back-Shifted Fermi Gas Model and Nuclear Level Density

Nuclear level density (NLD) represents an important ingredient for the theory of nuclear reactions. In most of the cases relevant to nuclear astrophysics, where experimental information is not available, the reaction rates for medium and heavy nuclei can only be estimated using the Hauser-Feshbach approach, which requires the knowledge of NLDs. In this research, we use NLDs calculated within the Shell Model approach and compare them with~the~standard phenomenological approaches, such as Fermi-Gas and Back-Shifted Fermi-Gas models. The more specific goal of this research is to fit the parameters of these phenomenological approaches,~such as temperature parameter,~and~to~study their behavior~across the~nuclei~in~\textit{sd-}shell~model space. We also studied the~effect~of pairing correlations~on~level density. We found that the~pairing gap parameter, which is usually introduced to take into account the~odd-even effect, does not cause much impact~on~the value of the~temperature~parameters.