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Nuclear Theory·nucl-th

Thursday·August 28, 2025

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 01

    Weighted Levenberg-Marquardt methods for fitting multichannel nuclear cross section data

    M. Imbrišak · A. E. Lovell · M. R. Mumpower

    We present an extension of the Levenberg-Marquardt algorithm for fitting multichannel nuclear cross section data. Our approach offers a practical and robust alternative to conventional trust-region methods for analyzing experimental data. The CoH code, based on the Hauser-Feshbach statistical model, involves a large number of interdependent parameters, making optimization challenging due to the presence of "sloppy" directions in parameter space. To address the uneven distribution of experimental data across reaction channels, we construct a weighted Fisher Information Metric by integrating prior distributions over dataset weights. This framework enables a more balanced treatment of heterogeneous data, improving both parameter estimation and convergence robustness. We show that the resulting weighted Levenberg-Marquardt method yields more physically consistent fits for both raw and smoothed datasets, using experimental data for Sm as a representative example. Additionally, we introduce a geometric scaling strategy to accelerate convergence -- a method based on the local geometry of the manifold.

    nucl-thstat.ML0 citations
  2. 02

    An optical-lensing inspired data thinning method for nuclear cross section data

    M. Imbrišak · A. E. Lovell · M. R. Mumpower

    In the study of nuclear cross sections, the computational demands of data assimilation methods can become prohibitive when dealing with large data sets. We have developed a novel variant of the data thinning algorithm, inspired by the principles of optical lensing, which effectively reduces data volume while preserving critical information. We show how it improves fitting through a toy problem and for several examples of total cross sections for neutron-induced reactions on rare-earth isotopes. We demonstrate how this method can be applied as an efficient pre-processing step prior to smoothing, significantly improving computational efficiency without compromising the quality of uncertainty quantification.

    nucl-th0 citations
  3. 03

    Reducing parametric uncertainties through information geometry methods

    M. Imbrišak · A. E. Lovell · M. R. Mumpower

    Information geometry is a study of applying differential geometry methods to challenging statistical problems, such as uncertainty quantification. In this work, we use information geometry to study how measurement uncertainties in pre-neutron emission mass distributions affect the parameter estimation in the Hauser-Feshbach fission fragment decay code, CGMF. We quantify the impact of reduced uncertainties on the pre-neutron mass yield of specific masses to these parameters, for spontaneous fission of Cf, first using a toy model assuming Poissonian uncertainties, then an experimental measurement taken from Göök et al., 2014 in EXFOR. We achieved a reduction of up to in CGMF parameter errors, predominantly in and .

    nucl-th0 citations
  4. 04

    and potentials in dense matter based on chiral EFT: Bridging heavy-ion collisions, hypernuclei, and neutron stars

    Asanosuke Jinno🇯🇵 · Koichi Murase🇯🇵 · Yasushi Nara🇯🇵 · Johann Haidenbauer🇩🇪

    The and directed flows at are investigated to examine their sensitivity to the hyperon single-particle potentials. The single-particle potentials are obtained from -matrix calculations with two- and three-body forces based on SU(3) chiral effective field theory. The directed flow shows sensitivity to the variation in the single-particle potential. Its effect is more pronounced for the directed flow.

    nucl-thEPJ Web Conf.(2026)·2 citations
  5. 05

    A comparison study of collisions at relativistic energies involving light nuclei

    Hai-Cheng Wang🇨🇳 · Song-Jie Li🇨🇳 · Jun Xu🇨🇳 · Zhong-Zhou Ren🇨🇳

    We present extensive comparisons of O+O collisions at the center-of-mass energy per nucleon pair GeV and Pb+O collisions at GeV as well as Ne+Ne collisions at GeV and Pb+Ne collisions at GeV based on a multiphase transport (AMPT) model. We recommend measuring the ratio of the elliptic flow to the triangular flow, which shows appreciable sensitivity to the structure of light nuclei as also found in other studies. This is especially so if the observable is measured near the target rapidity in Pb+O or Pb+Ne collisions, as originally found in the present study. Our study serves as a useful reference for understanding the structure effect on observables in collisions involving light nuclei under analysis or on the schedule.

    nucl-thhep-exnucl-exUniverse(2025)·1 citation
  6. 06

    Topological Uncertainty for Anomaly Detection in the Neural-network EoS Inference with Neutron Star Data

    Kenji Fukushima · Syo Kamata

    We study the performance of the Topological Uncertainty (TU) constructed with a trained feedforward neural network (FNN) for Anomaly Detection. Generally, meaningful information can be stored in the hidden layers of the trained FNN, and the TU implementation is one tractable recipe to extract buried information by means of the Topological Data Analysis. We explicate the concept of the TU and the numerical procedures. Then, for a concrete demonstration of the performance test, we employ the Neutron Star data used for inference of the equation of state (EoS). For the training dataset consisting of the input (Neutron Star data) and the output (EoS parameters), we can compare the inferred EoSs and the exact answers to classify the data with the label . The subdataset with leads to the normal inference for which the inferred EoS approximates the answer well, while the subdataset with ends up with the unsuccessful inference. Once the TU is prepared based on the -labled subdatasets, we introduce the cross-TU to quantify the uncertainty of characterizing the -labeled data with the label . The anomaly or unsuccessful inference is correctly detected if the cross-TU for is smaller than that for and . In our numerical experiment, for various input data, we calculate the cross-TU and estimate the performance of Anomaly Detection. We find that performance depends on FNN hyperparameters, and the success rate of Anomaly Detection exceeds in the best case. We finally discuss further potential of the TU application to retrieve the information hidden in the trained FNN.

    nucl-thcs.AIcs.LG0 citations
  7. 07

    Microscopic nuclear structure study of Th by Projected Shell Model

    Zi-Rui Chen · Long-Jun Wang · Yuanbin Wu

    Th, a crucial candidate for nuclear clocks and many other applications, is a typical heavy nucleus with an extremely low-energy isomeric state Th. A detailed study of the nuclear structure of Th is performed here by the microscopic model of state-of-the-art projected shell model. Our calculation describes well low-energy levels of Th, and provides a reduced transition probability of W.u. for the isomeric transition which agrees well with the radiative lifetime of Th measured recently. Our result supports a small multipole mixing for the cross-band transition of the second-excited state of Th, suggesting that further investigations on the inconsistencies in the decay of the second-excited state should be necessary. The physics behind these properties is revealed by the analysis of the nuclear wave functions. Our findings provide a deep insight into Th from the microscopic nuclear structure point of view, and offer the chance for further studies for nuclear clocks and relevant topics by microscopic nuclear structure theory.

    nucl-thPLB(2025)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE