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Nuclear Theory·nucl-th

Friday·June 12, 2026

13 papers—6 primary·7 cross-listed

All13Primary6Cross-lists7
  1. 01

    Analytic calculator for determination of -ray angular distribution coefficients and tensors in aligned and partially-aligned nuclei

    A.M. Hurst · D.A. Matters · T. Kawano

    A program has been developed to calculate a complete set of -ray angular distribution coefficients and statistical tensors in maximally- and partially-aligned nuclei. For practical nuclear structure and reaction purposes, there is no imposed constraint on any arguments that are likely to arise in the determination of these quantities. The program can also be used as a stand-alone vector-coupling calculator for the exact evaluation of Clebsch-Gordan and Racah coefficients, the closely-related Wigner 3-, 6-, and 9- symbols, as well as Gaunt coefficients. These quantities, which frequently arise in quantum mechanical applications involving angular momentum coupling and recoupling schemes, provide the underlying machinery in angular distribution calculations.

    nucl-th0 citations
  2. 02

    Efficient emulation of nuclear ground states with neural-network variational Monte Carlo and eigenvector continuation

    Mao Li · Yilong Yang · Pengwei Zhao

    An efficient emulator for \emph{ab initio} calculations of nuclear ground-state properties is developed by integrating the neural-network variational Monte Carlo framework, FeynmanNet, with the eigenvector continuation. It enables the calculation of observables for different Hamiltonians with minimal computational cost, while delivering ground-state energies with errors below compared to the full FeynmanNet results. With this emulator, the ground-state energies and charge radii of , , , , and are computed using a nuclear Hamiltonian derived from the leading-order pionless effective field theory, with a large number of different values of low-energy constants (LECs). Then, we perform a global sensitivity analysis of the ground-state energies, charge radii, separation energies of selected nuclei for the three LECs in the Hamiltonian, to identify how each LEC contributes to the variances of these observables. It shows that the two-body LEC in the channel is the most influential LEC governing these nuclear bulk properties. Finally, the correlations among the ground-state energies of He, C, and O are investigated by varying the LECs in the Hamiltonian. The analysis reveals that the experimental ground-state energies of C and O cannot be reproduced simultaneously by varying the LECs in the leading-order pionless Hamiltonian. This suggests that additional ingredients in the leading-order Hamiltonian are required to improve its description of light nuclei. The present work establishes an efficient framework for global sensitivity analysis and uncertainty quantification in the quantum Monte Carlo calculations for light and medium-mass nuclei.

    nucl-thPRC(2026)·2 citations
  3. 03

    The leading nuclear-structure electrostatic correction in arbitrary decays

    Daniel Benatar🇮🇱 · Ayala Glick-Magid🇮🇱 · Doron Gazit🇮🇱

    We develop a systematic theoretical framework to improve theoretical predictions for nuclear decays of arbitrary angular momentum , leading to a model-independent nuclear-structure electrostatic correction to the Coulomb interaction between the emitted lepton and the nuclear charge distribution, useful for ongoing and future precision searches for physics beyond the Standard Model. The formalism is based on nuclear matrix elements expanded in multipole operators, as commonly used in \emph{ab initio} calculations. First-order Coulomb corrections are derived from one-photon exchange preserving the full multipole and angular structure of the decay rate, and are subsequently expanded in the relevant small parameters of the nuclear problem, suppressing the leading nuclear structure correction to a few per-mills for medium mass nuclei with natural beta decay properties. We show that within this formalism, the leading Coulomb correction originates from three modifications of the original weak-only interaction: a modification of the nuclear charge form factor, which yields a correction similar to the known Fermi function, a shift of the momentum transfer within the lepton traces, and the same shift but inside the nuclear multipole operators. We additionally provide explicit results for allowed Gamow--Teller and unique first-forbidden transitions.

    nucl-thhep-phnucl-ex1 citation
  4. 04

    Hadron polarization and equation of state at FAIR/RHIC-BES energies

    Dai-Neng Liu · Jan Steinheimer · Kai-Jia Sun🇨🇳 · Jin-Hui Chen🇨🇳 · Yu-Gang Ma🇨🇳 · Marcus Bleicher🇩🇪

    The global polarization indicates that hot and dense matter created in non-central heavy-ion collisions carries large orbital angular momentum. However, the relation between hadronic polarization and the medium's collective rotation remains to be validated. Using the UrQMD transport model, we calculate the thermal vorticity-induced polarization of s in Ag+Ag and Au+Au collisions from - GeV and a range of centralities. Two different equations of state used in the UrQMD simulation are compared: one resembles a hadron resonance gas, while the other is based on the chiral mean field (CMF) model, providing a more realistic description of dense nuclear matter including a chiral transition that is consistent with lattice QCD expectations. The polarization is sensitive to the equation of state and a softer EoS leads to smaller values. In addition, we show that the polarization in the experimental acceptance and centrality selection does not decrease for even lower beam energies. Our results indicate that the process leading to the large vorticity is a result of the large shear in the baryon current created by its stopping.

    nucl-th0 citations
  5. 05

    Transport simulations with a constrained momentum-dependent Chiral Mean Field EoS at different iso-spin fractions

    Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪

    We present a comparison of the UrQMD model using a chiral mean field EoS (CMF) with flow and pion production data in heavy ion collisions at low beam energies GeV and varying iso-spin fraction. The CMF model parameters are constrained by known properties of the high density equation of state of QCD at varying iso-spin fractions. This allows us to calculate the equation of state as well as nuclear interactions for different physical systems like neutron stars and heavy ion collisions in a consistent way. It is found that heavy ion reactions at the upcoming FAIR facility will only have marginal sensitivity on the iso-spin dependence of the high-density equation of state. At lower beam energies, comparing to FOPI, HADES and Srit data, the sensitivity is higher but the observed deviations and systematic uncertainties of the existing data are larger than the sensitivity to the symmetry energy.

    nucl-th1 citation
  6. 06

    Observable Dependence of Viscous Corrections in QGP: Heavy Quarks and Dileptons in Chapman--Enskog Theory

    Lakshmi J. Naik · P. Parvathi · Nachiketa Sarkar · V. Sreekanth

    We calculate, for the first time, heavy quark transport and thermal dilepton production from QGP using viscous correction up to second order in gradients. We use the form of viscous correction obtained from Chapman-Enskog like expansion of the Boltzmann transport equation in relaxation time approximation, and compare our results with that of Grad's 14-moment approximation. By employing the temperature and shear stress evolution profiles of QGP obtained from second-order causal relativistic viscous hydrodynamics, we study the heavy quark transport coefficients and thermal dilepton production from an evolving QGP. In the case of HQ transport, the CE corrections suppress the drag force substantially, induce a non-trivial momentum dependence in transverse momentum diffusion, and result in a comparatively less modification in longitudinal momentum diffusion. Whereas, for thermal dileptons, the CE corrections result in an enhanced early-time contribution which decreases and become converging to the first-order CE correction with the evolution of QGP, and remain well behaved compared to that of Grad's correction. Our results indicate that the modification of the observable due to viscous corrections is governed by the magnitude of the corrections as well as the interplay between their momentum dependence and momentum weighting of the transport and emission kernels. We demonstrate that the momentum structure of the various viscous corrections at the level of distribution function is not directly translated to the observables since the different observables are sensitive to distinct regions of momentum space.

    nucl-thhep-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE