Nuclear Theory·nucl-th

Monday·September 2, 2024

5 papers—5 primary·0 cross-listed

01
[Submitted on 29 Aug 2024]
Longitudinal form factors of $A \leq 10$ nuclei in a chiral effective field theory approach
G. B. King🇺🇸 · G. Chambers-Wall🇺🇸 · A. Gnech🇺🇸 · S. Pastore🇺🇸 · M. Piarulli🇺🇸 · R. B. Wiringa🇺🇸
In this work, we present the elastic electron scattering longitudinal form factors of $A \leq 10$ nuclei computed in a variational Monte Carlo approach. We employ the Norfolk family of local chiral interactions and a consistent electromagnetic charge operator. Our calculations are compared both to data and past theoretical evaluations. This work represents, to our knowledge, the first exact many-body calculation of longitudinal form factors in the $7 \leq A \leq 10$ mass range. Finally, we identify $^{9}$ Be and $^{10}$ B as candidate targets for renewed experimental interest, as they exhibit the potential to provide more stringent constraints on the theoretical models.
Comments:
12 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2408.16909 [pdf]
PRC(2024)·7 citations
02
[Submitted on 30 Aug 2024]
Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectilelike fragments
Lei Shen · Akira Ono · Yu-Gang Ma
Molecular dynamics approaches use wave packets as nucleon wave functions to simulate the time evolution of nuclear reactions. It is crucial to activate the momentum fluctuation inherent in each wave packet so that it properly affects the time evolution. In the antisymmetrized molecular dynamics (AMD) model, this has traditionally been done by splitting the wave packets, i.e., by introducing a random fluctuation to the wave packet center of each particle. The present work proposes an improved approach to activate the fluctuation in both the one-body mean-field propagation and the two-nucleon collision processes, consistently based on the gradual or sudden change of the degree of isolation, which is derived from the fragment number function used for the zero-point energy subtraction. This new method is applied to the 12C + 12C and 12C + p reactions at about 100 MeV/nucleon, focusing on the momentum distribution of the 11B fragments produced by one-proton removal from the 12C projectile. The results show that, with the momentum fluctuation suitably activated, the method correctly accounts for the recoil from the removed nucleon to the residue and the 11B momentum distribution is significantly improved, while without activating the fluctuation the distribution is too narrow compared to the experimental data. Furthermore, the AMD results indicate that the momentum distribution consists of two components; one is the high $P_{z}$ component with a small shift from the beam velocity, resulting from the simple removal of a proton after an energetic collision with a target particle; the other is the low $P_{z}$ component with a larger peak shift resulting from the decay of an excited 12C nucleus in a longer time scale. The activation of momentum fluctuation mainly affects the high $P_{z}$ component to broaden it. The role of cluster correlations in this problem is also investigated.
Comments:
15 pages, 16 figures, version accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2408.17029 [pdf]
PRC(2024)·2 citations
03
[Submitted on 30 Aug 2024]
Exploring the effect of positive Q-value neutron transfer in coupled-channels calculations using microscopic nuclear potentials
N. Jain · M. Bhuyan · P. Mohr · Raj Kumar
We investigated the effect of the degree of freedom of neutron transfer on the cross section of heavy-ion fusion reactions, using the relativistic mean-field formalism within the coupled channel approach (CCFULL). We obtain the microscopic nuclear interaction potential in terms of the density distributions for the targets and projectiles with the NL3 $^{*}$ parameter set and corresponding R3Y nucleon-nucleon potential. The present analysis includes the $^{18}$ O-induced reactions, for which experimental fusion cross-section is available around the Coulomb barrier. It is evident from the results that including vibrational and/or rotational degrees of freedom enhances the fusion cross-section at energies below the barrier. However, fusion hindrance persists in this energy region. To address this, we incorporated the two-neutron $(2 n)$ transfer channels in the Coupled Channel calculation. A comparison with the Woods-Saxon potential (WS) shows that the R3Y nucleon-nucleon (NN) potential, with intrinsic degrees of freedom, is superior to it, especially at energies below the barrier. This superiority can be attributed to the observed higher barrier heights and lower cross-section of the WS potential compared to the relativistic R3Y NN potential for the considered reaction systems. Consequently, we employed the relativistic mean-field formalism to estimate fusion characteristics for the unknown $^{18}$ O-induced reactions, namely $^{18}$ O + $^{62}$ {Ni}, $^{18}$ O + $^{70, 72, 76}$ {Ge}, $^{18}$ O + $^{144, 150}$ {Nd}, and $^{18}$ O + $^{144, 148, 152, 154}$ {Sm}. Our analysis highlights the significant role of positive $Q$ -value neutron transfer in enhancing the sub-barrier fusion cross-section for the $^{18}$ O + $^{148}$ {Nd} reaction with the R3Y NN potential. However, the effect of this transfer channel for the other considered reactions is comparatively less pronounced.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2408.17291 [pdf]
PRC(2024)·3 citations
04
[Submitted on 30 Aug 2024]
Neutron-proton pairing correlations described on quantum computers
Jing Zhang🇫🇷 · Denis Lacroix🇫🇷 · Yann Beaujeault-Taudiere🇫🇷
The ADAPT-VQE approach is used to solve the neutron-proton pairing problem in atomic nuclei. This variational approach is considered today as one of the most powerful methods to iteratively find the ground state of a many-body problem, provided a performing set of operators, called the pool of operators, is used to explore the Hilbert space of many-body wave-functions. Three different pools of operators, which might eventually break one or several symmetries of the Hamiltonian during the descent to the ground state, are tested for the neutron-proton pairing problem. We observe that the breaking of some symmetries during the optimization of the trial wave-function might, in general, help to speed up the convergence towards the ground state. Still, we rejected the pool of operators that might explicitly break the total particle number because they become uncontrollable during the optimization process. Overall, we observed that the iterative optimization process rapidly becomes a delicate problem when the number of parameters to build the ansatz increases, and the energy might get stuck at energies higher than the ground state energy. To improve the convergence in this case, several techniques have been proposed, with some better controlling the symmetries during the energy minimization. Among the proposed methods, two have proven effective: one based on an embedding technique and the other on a randomized preparation of the initial state. We conclude that the ADAPT-VQE, complemented by these techniques, can provide a very accurate description of the neutron-proton pairing problem, and can outperform other standardly used techniques that break the particle number symmetry and restore afterwards.
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2408.17294 [pdf]
PRC(2024)·15 citations
05
[Submitted on 30 Aug 2024]
How do mirror charge radii constrain density dependence of the symmetry energy?
Bai-Shan Hu🇨🇦
It has recently been suggested that differences in the charge radii of mirror nuclei ( $Δ R_{ch}^{mirr}$ ) are strongly correlated with the neutron-skin thickness ( $R_{skin}$ ) of neutron-rich nuclei and with the slope of the symmetry energy ( $L$ ). To test this assumption, we present ab initio calculations of $R_{skin}$ in $^{48}$ Ca and $^{208}$ Pb, $Δ R_{ch}^{mirr}$ in $^{36}$ Ca $-^{36}$ S, $^{38}$ Ca $-^{38}$ Ar, $^{41}$ Sc $-^{41}$ Ca, $^{48}$ Ni $-^{48}$ Ca, $^{52}$ Ni $-^{52}$ Cr, and $^{54}$ Ni $-^{54}$ Fe mirror pairs, and $L$ . Employing the recently developed 34 chiral interaction samples, identified by the history matching approach, we conduct rigorous statistical analysis of correlations among $Δ R_{ch}^{mirr}$ , $R_{skin}$ and $L$ , accounting for quantified uncertainties from low-energy constants of chiral interaction, chiral effective field theory truncation and many-body method approximation. The ab initio results reveal an appreciable $Δ R_{ch}^{mirr} - L$ correlation in $f p$ -shell mirror pairs. However, contrary to previous studies, the present calculation finds that the studied $s d$ -shell mirror pairs do not exhibit any $Δ R_{ch}^{mirr} - L$ correlation.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2408.17403 [pdf]
PLB(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Longitudinal form factors of A≤10 nuclei in a chiral effective field theory approach

Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectilelike fragments

Exploring the effect of positive Q-value neutron transfer in coupled-channels calculations using microscopic nuclear potentials

Neutron-proton pairing correlations described on quantum computers

How do mirror charge radii constrain density dependence of the symmetry energy?

Affiliations

Longitudinal form factors of $A \leq 10$ nuclei in a chiral effective field theory approach