Stochastic estimation of nuclear level density in the nuclear shell model; An Application to parity-dependent level density in Ni

Shimizu, Noritaka*; Utsuno, Yutaka   ; Futamura, Yasunori*; Sakurai, Tetsuya*; Mizusaki, Takahiro*; Otsuka, Takaharu*

Nuclear level density plays an important role in applications to nuclear energy and nuclear astrophysics, dominating neutron-capture cross sections. In this paper, we propose a new, practical and accurate method of estimating nuclear level density within the framework of the nuclear shell model, and show its feasibility and usefulness. This method is based on the idea that the level density is obtained by the number of eigenstates that is represented as a contour integral in the complex plane. We first confirm the feasibility of this method using a small system in which the exact eigenstates are available, and then calculate parity-dependent level density in Ni, which cannot be calculated with direct eigenstate counting. We succeed in reproducing the experimental result that the and level densities are almost identical in low-energy regions, which cannot be obtained with conventional methods of estimating level densities.