Calculation of cross section in resonance region using the statistical properties of the resonance parameters

Furutachi, Naoya; Minato, Futoshi   ; Iwamoto, Osamu  

Except for extremely light nuclei and neutron rich nuclei, generally the density of nuclear excited states around neutron threshold energy is very high, and therefore it is very difficult to predict energy and width of resonance precisely. On the other hand, it has been known that the resonance parameters have statistical property with high density of excited states. There is a theoretical method to calculate cross section in resonance region by generating resonance parameters randomly utilizing the statistical properties of the resonance parameters. Such a method can reflect a theoretical information of resonance on a nuclear data evaluation for nuclei with no experimental data, such as fission products. However, studies for how to determine a representative value of the cross section randomly calculated, and what is an uncertainty from the randomness, are insufficient. Therefore, in this study, we calculated the cross section in the resonance region using randomly generated resonance parameters, and derived the probability distribution of the cross section by calculating cross section repetitively using resonance parameter sets generated from different random seeds. By using this density distribution, we discuss the behavior of the statistically reasonable cross section, and uncertainty from statistical fluctuation.