Simultaneous fitting of statistical-model parameters to symmetric and asymmetric fission cross sections

TL;DR

This paper proposes a method to simultaneously fit statistical model parameters to both symmetric and asymmetric fission cross sections, improving the predictive power of nuclear de-excitation models.

Contribution

It introduces a strategy to constrain model parameters using multiple entrance channels, including fusion and spallation, for a unified description of nuclear fission.

Findings

Effective parameter constraints for fission cross sections

Enhanced predictive accuracy of GEMINI++ model

Unified description of nuclear de-excitation processes

Abstract

The de-excitation of compound nuclei has been successfully described for several decades by means of statistical models. However, accurate predictions require some fine-tuning of the model parameters. This task can be simplified by studying several entrance channels, which populate different regions of the parameter space of the compound nucleus. Fusion reactions play an important role in this strategy because they minimise the uncertainty on the entrance channel by fixing mass, charge and excitation energy of the compound nucleus. If incomplete fusion is negligible, the only uncertainty on the compound nucleus comes from the spin distribution. However, some de-excitation channels, such as fission, are quite sensitive to spin. Other entrance channels can then be used to discriminate between equivalent parameter sets. The focus of this work is on fission and intermediate-mass-fragment emission cross sections of compound nuclei with 70<=A<=240. The statistical de-excitation model is GEMINI++. The choice of the observables is natural in the framework of GEMINI++, which describes fragment emission using a fission-like formalism. Equivalent parameter sets for fusion reactions can be resolved using the spallation entrance channel. This promising strategy can lead to the identification of a minimal set of physical ingredients necessary for a unified quantitative description of nuclear de-excitation.