Statistical double Λ hypernuclear formation from Ξ− absorption at rest in light nuclei

We investigate double $\Lambda$ hyperfragment formation from the statistical decay of double $\Lambda$ compound nuclei produced in the $\Xi^-$ absorption at rest in the light nuclei $^{12}\mathrm{C}$, $^{14}\mathrm{N}$, and $^{16}\mathrm{O}$. We examine the target and the $\Lambda\Lambda$ bond energy dependence of the double $\Lambda$ hyperfragment formation probabilities, especially of those double hypernuclei observed in experiments. For the $^{12}\mathrm{C}$ ($^{14}\mathrm{N}$) target, the formation probabilities of $^{\,\;\;6}_{\Lambda\Lambda}\mathrm{He}$ and $^{\;10}_{\Lambda\Lambda}\mathrm{Be}$ ($^{\;13}_{\Lambda\Lambda}\mathrm{B}$) are found to be reasonably large as they are observed in the KEK-E373 (KEK-E176) experiment. By comparison, for the $^{16}\mathrm{O}$ target, the formation probability of $^{\;11}_{\Lambda\Lambda}\mathrm{Be}$ is calculated to be small with $\Delta B_{\Lambda\Lambda}$ consistent with the Nagara event. We also evaluate the formation probability of ${}^{\,\;\;5}_{\Lambda\Lambda}\mathrm{H}$ from a $\Xi^-$–${}^{6}\mathrm{He}$ bound state, ${}^{7}_{\Xi}\mathrm{H}$.

The fission yield calculations with Langevin model, Hauser-Feshbach statistical decay, and beta decay

We performed the calculations of de-excitation of the primary fission fragments by the Hauser-Feshbach statistical decay followed by the β decay of de-excited fission products. We used the primary fission fragment mass distributions YP(A), total kinetic energy TKE(A), and its width σTKE(A) as input, which were calculated with the Langevin model using macroscopic-microscopic models of the potential energy surface. The prompt neutron multiplicity v̅ and the independent fission product yield (FPY) YI(Z, A, M) and cumulative FPY YC(Z, A, M) are calculated by the Hauser-Feshbach statistical decay and β decay calculations, respectively. The calculated v̅ was overestimated approximately 17% compared to the evaluated data. The decay heats from β and γ were in accordance with the experimental results. The β delayed neutrons yieild was also overestimated.

Prompt and Delayed Neutron Emissions and Fission Product Yield Calculations with Hauser-Feshbach Statistical Decay Theory and Summation Calculation Method

We demonstrate the neutron emission and fission product yield calculations using the Hauser–Feshbach Fission Fragment Decay (HF3D) model and β decay. The HF3D model calculates the statistical decay of more than 500 primary fission fragment pairs formed by the neutron induced fission of 235U. In order to calculate the prompt neutron and photon emissions, the primary fission fragment distributions, i.e. mass, charge, excitation energy, spin and parity are deterministically generated and numerically integrated for all fission fragments. The calculated prompt neutron multiplicities, independent fission product yield are fully consistent each other. We combine the β-decay and the summation calculations with the HF3D model calculation to obtain the cumulative fission product yield, decay heat and delayed neutron yield. The calculated fission observables are compared with available experimental data.

Implementing and testing theoretical fission fragment yields in a Hauser-Feshbach statistical decay framework

We implement fission fragment yields, calculated using Brownian shape-motion on a macroscopic-microscopic potential energy surface in six dimensions, into the Hauser-Feshbach statistical decay code CGMF. This combination allows us to test the impact of utilizing theoretically-calculated fission fragment yields on the subsequent prompt neutron and γ-ray emission. We draw connections between the fragment yields and the total kinetic energy TKE of the fission fragments and demonstrate that the use of calculated yields can introduce a difference in the 〈TKE〉 and, thus, the prompt neutron multiplicity v, as compared with experimental fragment yields. We deduce the uncertainty on the 〈TKE〉 and v from this procedure and identify possible applications.