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Nuclear Theory·nucl-th

Wednesday·September 29, 2021

11 papers—6 primary·5 cross-listed

All11Primary6Cross-lists5
  1. 01

    The importance of few-nucleon forces in chiral effective field theory

    C.-J. Yang🇸🇪 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · G. Hagen🇺🇸 · G. Rupak🇺🇸 · U. van Kolck🇫🇷

    We study the importance of few-nucleon forces in chiral effective field theory for describing many-nucleon systems. A combinatorial argument suggests that three-nucleon forces -- which are conventionally regarded as next-to-next-to-leading order -- should accompany the two-nucleon force already at leading order (LO) starting with mass number . We find that this promotion enables the first realistic description of the O ground state based on a renormalization-group-invariant LO interaction. We also performed coupled-cluster calculations of the equation of state for symmetric nuclear matter and our results indicate that LO four-nucleon forces could play a crucial role for describing heavy-mass nuclei. The enhancement mechanism we found is very general and could be important also in other many-body problems.

    nucl-thEPJA(2023)·37 citations
  3. 03

    Multinucleon excitations in neutrino-nucleus scattering: connecting different microscopic models for the correlations

    G. Chanfray🇫🇷 · M. Ericson🇫🇷 · M. Martini🇫🇷

    The problem of nucleon-nucleon correlations and meson exchange currents has been vividly debated in connection with the neutrino-nucleus cross sections. In this work we focus on nucleon-nucleon correlations by discussing a formal correspondence between the approaches based on independent particles and the ab initio approaches involving correlated wave functions. We use a general technique based on unitary transformation mapping the Fermion operators relative to bare nucleons into quasi-particle operators relative to dressed nucleons. We derive formulas for spectral functions, response functions, momentum distribution, separation energy, general enough to be applied with any kind of effective nucleon-nucleon interaction. We establish the relation between the non-energy-weighted sum rule and the Fermi sea depopulation. With our tools we evaluate whether approaches based on effective interactions are compatible with the expected amount of correlations coming from ab initio calculations. For this purpose we use as a test the Fermi sea depopulation and the value of the kinetic energy per nucleon.

    nucl-thEur.Phys.J.ST(2021)·5 citations
  4. 04

    Uncertainties in the pasta-phase properties of catalysed neutron stars

    H. Dinh Thi🇫🇷 · T. Carreau🇫🇷 · A. F. Fantina🇫🇷 · F. Gulminelli🇫🇷

    The interior of a neutron star is expected to exhibit different states of matter. In particular, complex non-spherical configurations known as `pasta' phases may exist at the highest densities in the inner crust, potentially having an impact on different neutron-star phenomena. We study the properties of the pasta phase and the uncertainties in the pasta observables which are due to our incomplete knowledge of the nuclear energy functional. To this aim, we employed a compressible liquid-drop model approach with surface parameters optimised either on experimental nuclear masses or theoretical calculations. To assess the model uncertainties, we performed a Bayesian analysis by largely varying the model parameters using uniform priors, and generating posterior distributions with filters accounting for both our present low-density nuclear physics knowledge and high-density neutron-star physics constraints. Our results show that the nuclear physics constraints, such as the neutron-matter equation of state at very low density and the experimental mass measurements, are crucial in determining the crustal and pasta observables. Accounting for all constraints, we demonstrate that the presence of pasta phases is robustly predicted in an important fraction of the inner crust. We estimate the relative crustal thickness associated with pasta phases as and the relative moment of inertia as . Our findings indicate that the surface and curvature parameters are more influential than the bulk parameters for the description of pasta observables. We also show that using a surface tension that is inconsistent with the bulk functional leads to an underestimation of both the average values and the uncertainties in the pasta properties, thus highlighting the importance of a consistent calculation of the nuclear functional.

    nucl-thastro-ph.HEAstron.Astrophys.(2021)·63 citations
  5. 05

    Theoretical study on favored alpha-decay half-lives of deformed nuclei

    M. Hassanzad · O. N. Ghodsi

    A systematic study on -decay half-lives for the nuclei in the range is done by employing various versions of proximity potentials. To obtain the more reliable results, the deformation terms are included up to hexadecapole () in the spherical-deformed nuclear and Coulomb interaction potentials. The favored -decays process in this region are categorized as the even-even, odd A, and odd-odd nuclei, first, and second they are grouped into two parts as a ground state to ground state and ground state to isomeric states transition. Due to their root-mean-square deviations (RMSD's) comparison, and have the least values and better compromise in reproducing experimental data. Besides, by considering preformation probability within the cluster formation model, the results validate that the significant reduction in root-mean-square deviations has been obtained for different versions of proximity; Hence detract the deviation between calculated and experimental data.

    nucl-thCPC(2021)·3 citations
  6. 06

    Optical potential parameters of light nuclear fusion based on precise Coulomb wave functions

    Binbing Wu · Hao Duan · Jie Liu

    Based on precise Coulomb wave functions (CWFs), we attempt to calculate the fusion cross sections of light nuclei in a complex spherical square-well nuclear potential (i.e., optical potential model). Comparing with experimental benchmark cross section data, we can calibrate optical potential parameters associated with D+D, D+T, D+3He, p+D, p+6Li and p+7Li fusion reactions. Surprisingly, we find that our calculated optical potential parameters are quite different from those of many previous results (e.g., Phys. Rev. C. 61 (2000) 024610, Nucl. Phys. A 986 (2019) 98, etc.), in which approximate Coulomb wave functions (ACWFs) with only retaining the leading terms are exploited for the continuity conditions at the radius of nuclear potential. Furthermore, with the obtained optical potential parameters, we compare the fusion cross sections and astrophysical S-factors with that formulated from ACWFs approach, and also find apparent deviations especially for the fusion reactions with resonance peaks such as D+T and D+3He fusion reactions. We then calculate the phase diagrams of the fusion cross sections with respect to the optical potential parameters and demonstrate several narrow shape resonance belts. It implies that a small deviation of ACWFs from the exact CWFs at nuclear radius might lead to fall off the resonance regimes and therefore causes the big difference on the optical parameters as well as the cross sections.

    nucl-thNPA(2022)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE