Nuclear Theory·nucl-th

Tuesday·February 16, 2016

7 papers—5 primary·2 cross-listed

01
[Submitted on 13 Feb 2016]
Capture cross sections of 15N(n, {\gamma})16N at astrophysical energies
Guang-wei Fan · Jun-bing Ma · Zong-qiang Sheng · Feng Tian · Jun Wang · Chao Zhang
We have reanalyzed reaction cross sections of 16N on 12C target. The nucleon density distribution of 16N, especially surface density distribution, was extracted using the modified Glauber model. On the basis of dilute surface densities, the discussion of 15N(n, {\gamma})16N reaction was performed within the framework of the direct capture reaction mechanism. The calculations agreed quite well with the experimental data.
Comments:
5 pages, 3 figures. arXiv admin note: text overlap with arXiv:0810.3867 by other authors
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.04338 [pdf]
CPC(2016)·0 citations
02
[Submitted on 13 Feb 2016]
Deuteron-induced nucleon transfer reactions within an ab initio framework: First application to p-shell nuclei
Francesco Raimondi🇨🇦 · Guillaume Hupin🇺🇸 · Petr Navrátil🇨🇦 · Sofia Quaglioni🇺🇸
Background: Low-energy transfer reactions in which a proton is stripped from a deuteron projectile and dropped into a target play a crucial role in the formation of nuclei in both primordial and stellar nucleosynthesis, as well as in the study of exotic nuclei using radioactive beam facilities and inverse kinematics. Ab initio approaches have been successfully applied to describe the $^{3}$ H $(d, n)^{4}$ He and $^{3}$ He $(d, p)^{4}$ He fusion processes. Purpose: An ab initio treatment of transfer reactions would also be desirable for heavier targets. In this work, we extend the ab initio description of $(d, p)$ reactions to processes with light $p$ -shell nuclei. As a first application, we study the elastic scattering of deuterium on $^{7}$ Li and the $^{7}$ Li( $d$ , $p$ ) $^{8}$ Li transfer reaction based on a two-body Hamiltonian. Methods: We use the no-core shell model to compute the wave functions of the nuclei involved in the reaction, and describe the dynamics between targets and projectiles with the help of microscopic-cluster states in the spirit of the resonating group method. Results: The shape of the excitation functions for deuteron impinging on $^{7}$ Li are qualitatively reproduced up to the deuteron breakup energy. The interplay between $d$ - $^{7}$ Li and $p$ - $^{8}$ Li particle-decay channels determines some features of the $^{9}$ Be spectrum above the $d$ + $^{7}$ Li threshold. Our prediction for the parity of the 17.298 MeV resonance is at odds with the experimental assignment Conclusions: Deuteron stripping reactions with $p$ -shell targets can now be computed ab initio, but calculations are very demanding. A quantitative description of the $^{7}$ Li( $d$ , $p$ ) $^{8}$ Li reaction will require further work to include the effect of three-nucleon forces and additional decay channels, and improve the convergence rate of our calculations.
Comments:
16 pages, 11 figures, submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.04404 [pdf]
PRC(2016)·26 citations
03
[Submitted on 14 Feb 2016]
Combined analysis of the $π^{-} p \to K^{0} Λ$ , $η n$ reactions in a chiral quark model
Li-Ye Xiao · Fan Ouyang · Xian-Hui Zhong
A combined analysis of the reactions $π^{-} p \to K^{0} Λ$ and $η n$ is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to $W ≃ 1.8$ GeV are reasonably described. For $π^{-} p \to K^{0} Λ$ , it is found that $N (1535) S_{11}$ and $N (1650) S_{11}$ paly crucial roles near threshold. The $N (1650) S_{11}$ resonance contributes to the reaction through configuration mixing with $N (1535) S_{11}$ . The constructive interference between $N (1535) S_{11}$ and $N (1650) S_{11}$ is responsible for the peak structure around threshold in the total cross section. The $n$ -pole, $u$ - and $t$ -channel backgrounds provide significant contributions to the reaction as well. While, for the $π^{-} p \to η n$ process, the "first peak" in the total cross section is dominant by $N (1535) S_{11}$ , which has a sizeable destructive interference with $N (1650) S_{11}$ . Around $P_{π} ≃$ 1.0 GeV/c ( $W ≃ 1.7$ GeV), there seems to be a small bump structure in the total cross section, which might be explained by the interference between the $u$ -channel and $N (1650) S_{11}$ . The $N (1520) D_{13}$ resonance notably affects the angle distributions of the cross sections, although less effects are seen in the total cross section. The role of $P$ -wave state $N (1720) P_{13}$ should be further confirmed by future experiments. If $N (1720) P_{13}$ has a narrow width of $Γ ≃ 120$ MeV as found in our previous work by a study of the $π^{0}$ photoproduction processes, obvious evidence should be seen in the $π^{-} p \to K^{0} Λ$ and $η n$ processes as well.
Comments:
12 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1602.04455 [pdf]
PRC(2016)·8 citations
04
[Submitted on 15 Feb 2016]
Nuclear binding near a quantum phase transition
Serdar Elhatisari🇩🇪 · Ning Li🇩🇪 · Alexander Rokash🇩🇪 · Jose Manuel Alarcón🇩🇪 · Dechuan Du🇩🇪 · Nico Klein🇩🇪 · Bing-nan Lu🇩🇪 · Ulf-G. Meißner🇩🇪 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Gautam Rupak🇺🇸
How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (4He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.
Comments:
Published version to appear in Physical Review Letters. Main: 5 pages, 3 figures. Supplemental material: 13 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex)
arXiv:
1602.04539 [pdf]
PRL(2016)·123 citations
05
[Submitted on 15 Feb 2016]
Medium polarization in asymmetric nuclear matter
S. S. Zhang🇨🇳 · L. G. Cao🇨🇳 · U. Lombardo🇮🇹 · P. Schuck🇫🇷
The influence of the core polarization on the effective nuclear interaction of asymmetric nuclear matter is calculated in the framework of the induced interaction theory. The strong isospin dependence of the density and spin density fluctuations is studied along with the interplay between the neutron and proton core polarizations. Moving from symmetric nuclear matter to pure neutron matter the crossover of the induced interaction from attractive to repulsive in the spin singlet state is determined as a function of the isospin imbalance.The density range in which it occurs is also determined. For the spin triplet state the induced interaction turns out to be always repulsive. The implications of the results for the neutron star superfluid phases are shortly discussed.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.04639 [pdf]
PRC(2016)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE

Capture cross sections of 15N(n, {\gamma})16N at astrophysical energies

Deuteron-induced nucleon transfer reactions within an ab initio framework: First application to p-shell nuclei

Combined analysis of the π−p→K0Λ, ηn reactions in a chiral quark model

Nuclear binding near a quantum phase transition

Medium polarization in asymmetric nuclear matter

Affiliations

Combined analysis of the $π^{-} p \to K^{0} Λ$ , $η n$ reactions in a chiral quark model