Nuclear Theory·nucl-th

Tuesday·August 25, 2015

18 papers—8 primary·10 cross-listed

01
[Submitted on 22 Aug 2015]
Roles of Antinucleon Degrees of Freedom in the Relativistic Random Phase Approximation
Haruki Kurasawa🇯🇵 · Toshio Suzuki🇯🇵
Roles of antinucleon degrees of freedom in the relativistic random phase approximation(RPA) are investigated. The energy-weighted sum of the RPA transition strengths is expressed in terms of the double commutator between the excitation operator and the Hamiltonian, as in nonrelativistic models. The commutator, however, should not be calculated with a usual way in the local field theory, because, otherwise, the sum vanishes. The sum value obtained correctly from the commutator is infinite, owing to the Dirac sea. Most of the previous calculations takes into account only a part of the nucleon-antinucleon states, in order to avoid the divergence problems. As a result, RPA states with negative excitation energy appear, which make the sum value vanish. Moreover, disregarding the divergence changes the sign of nuclear interactions in the RPA equation which describes the coupling of the nucleon particle-hole states with the nucleon-antinucleon states. Indeed, excitation energies of the spurious state and giant monopole states in the no-sea approximation are dominated by those unphysical changes. The baryon current conservation can be described without touching the divergence problems. A schematic model with separable interactions is presented, which makes the structure of the relativistic RPA transparent.
Comments:
21 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1508.05443 [pdf]
PTEP(2015)·1 citation
02
[Submitted on 22 Aug 2015]
Covariant energy density functionals: the assessment of global performance across the nuclear landscape
A.V.Afanasjev
The assessment of the global performance of the state-of-the-art covariant energy density functionals and related theoretical uncertainties in the description of ground state observables has recently been performed. Based on these results, the correlations between global description of binding energies and nuclear matter properties of covariant energy density functionals have been studied in this contribution.
Comments:
4 pages, 2 figures, Contribution to the Proceedings of the International Nuclear Physics Conference 'Nuclear Structure and Dynamics III', Portoroz, Slovenia, 2015
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1508.05526 [pdf]
AIP Conf.Proc.(2015)·0 citations
03
[Submitted on 23 Aug 2015]
Extended Hartree-Fock study of the single-particle potential: the nuclear symmetry energy, nucleon effective mass, and folding model of the nucleon optical potential
Doan Thi Loan · Bui Minh Loc · Dao T. Khoa
The nucleon mean-field potential has been thoroughly investigated in an extended Hartree-Fock (HF) calculation of nuclear matter (NM) using the CDM3Y3 and CDM3Y6 density dependent versions of the M3Y interaction. The single-particle (s/p) energies of nucleons in NM are determined according to the Hugenholtz-van Hove theorem, which gives rise naturally to a rearrangement term (RT) of the s/p potential at the Fermi momentum. Using the RT obtained exactly at the different NM densities and neutron-proton asymmetries, a consistent method is suggested to take into account effectively the momentum dependence of the RT of the s/p potential within the standard HF scheme. To obtain a realistic momentum dependence of the nucleon optical potential (OP), the high-momentum part of the s/p potential was accurately readjusted to reproduce the observed energy dependence of the nucleon OP over a wide range of energies. The impact of the RT and momentum dependence of the s/p potential on the density dependence of the nuclear symmetry energy and nucleon effective mass has been studied in details. The high-momentum tail of the s/p potential was found to have a sizable effect on the slope of the symmetry energy and the neutron-proton effective mass splitting at supranuclear densities of the NM. Based on a local density approximation, the folding model of the nucleon OP of finite nuclei has been extended to take into account consistently the RT and momentum dependence of the nucleon OP in the same mean-field manner, and successfully applied to study the elastic neutron scattering on the lead target at the energies around the Fermi energy.
Comments:
Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1508.05568 [pdf]
PRC(2015)·25 citations
04
[Submitted on 23 Aug 2015]
Correlations in light nuclei and their relation to fine tuning and uncertainty quantifications of many body forces in low-energy nuclear physics
Sergiu Lupu🇮🇱 · Nir Barnea🇮🇱 · Doron Gazit (Hebrew U.)🇮🇱
The large nucleon-nucleon scattering length, and the isospin approximate symmetry, are low energy properties of quantum chromodynamics (QCD). These entail correlations in the binding energies of light nuclei, e.g., the A=3 iso-multiplet, and Tjon's correlation between the binding energy of three and four body nuclei. Using a new representation of these, we establish that they translate into a correlation between different short-range contributions to three body forces in chiral effective field theory of low-energy nuclear physics. We demonstrate that these correlations should be taken into account in order to avoid fine-tuning in the calibration of three body forces. We relate this to the role of correlations in uncertainty quantification of non-renormalizable effective field theories of the nuclear regime. In addition, we show that correlations can be useful in assessing the importance of forces induced by renormalization group (RG) transformations. We give numerical evidence that such RG transformations can be represented effectively by adding a constant to the pure three nucleon contact low energy constant $c_{E}$ .
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1508.05654 [pdf]
2 citations
05
[Submitted on 24 Aug 2015]
Are there good probes for the di-neutron correlation in light neutron-rich nuclei?
K. Hagino · H. Sagawa
The di-neutron correlation is a spatial correlation with which two valence neutrons are located at a similar position inside a nucleus. We discuss possible experimental probes for the di-neutron correlation. This includes the Coulomb breakup and the pair transfer reactions of neutron-rich nuclei, and the direct two-neutron decays of nuclei beyond the neutron drip-line.
Comments:
9 pages, 5 figures. A talk given at the international workshop on weakly bound exotic nuclei (WBEN), May 24-30, 2015, Natal, Brazil. To be published in a special issue of Few-Body Systems
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1508.05700 [pdf]
Few Body Syst.(2016)·13 citations
06
[Submitted on 24 Aug 2015]
Effect of Wigner energy on the symmetry energy coefficient in nuclei
Junlong Tian · Haitao Cui · Teng Gao · Ning Wang
The nuclear symmetry energy coefficient (including the coefficient $a_{sym}^{(4)}$ of $I^{4}$ term) of finite nuclei is extracted by using the differences of available experimental binding energies of isobaric nuclei. It is found that the extracted symmetry energy coefficient $a_{sym}^{*} (A, I)$ decreases with increasing of isospin asymmetry $I$ , which is mainly caused by Wigner correction, since $e_{sym}^{*}$ is the summation of the traditional symmetry energy $e_{sym}$ and the Wigner energy $e_{W}$ . We obtain the optimal values $J = 30.25 \pm 0.10$ MeV, $a_{ss} = 56.18 \pm 1.25$ MeV, $a_{sym}^{(4)} = 8.33 \pm 1.21$ MeV and the Wigner parameter $x = 2.38 \pm 0.12$ through the polynomial fit to 2240 measured binding energies for nuclei with $20 \leq A \leq 261$ with an rms deviation of 23.42 keV. We also find that the volume symmetry coefficient $J ≃ 30$ MeV is insensitive to the value $x$ , whereas the surface symmetry coefficient $a_{ss}$ and the coefficient $a_{sym}^{(4)}$ are very sensitive to the value of $x$ in the range $1 \leq x \leq 4$ . The contribution of $a_{sym}^{(4)}$ term increases rapidly with increasing of isospin asymmetry $I$ . For very neutron-rich nuclei, the contribution of $a_{sym}^{(4)}$ term will play an important role.
Comments:
14 pages, 5 figures, Submitted to Chinese Physics C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1508.05780 [pdf]
CPC(2016)·9 citations
07
[Submitted on 24 Aug 2015]
MCNP6 simulation of light and medium nuclei fragmentation at intermediate energies
Stepan G. Mashnik · Leslie M. Kerby
Fragmentation reactions induced on light and medium nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the Los Alamos transport code MCNP6 and with its CEM03.03 and LAQGSM03.03 event generators. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after the INC. CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to 4He from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codes
Comments:
6 pages, 6 figures, proc. 12th Int. Conf. on Nucleus-Nucleus Collisions (NN2015), June 21-26, 2015, Catania, Italy
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1508.05875 [pdf]
EPJ Web Conf.(2016)·1 citation
08
[Submitted on 24 Aug 2015]
A viscous blast-wave model for relativistic heavy-ion collisions
Amaresh Jaiswal🇩🇪 · Volker Koch🇺🇸
Using a viscosity-based survival scale for geometrical perturbations formed in the early stages of relativistic heavy-ion collisions, we model the radial flow velocity during freeze-out. Subsequently, we employ the Cooper-Frye freeze-out prescription, with first-order viscous corrections to the distribution function, to obtain the transverse momentum distribution of particle yields and flow harmonics. For initial eccentricities, we use the results of Monte Carlo Glauber model. We fix the blast-wave model parameters by fitting the transverse momentum spectra of identified particles at the Large Hadron Collider (LHC) and demonstrate that this leads to a fairly good agreement with transverse momentum distribution of elliptic and triangular flow for various centralities. Within this viscous blast-wave model, we estimate the shear viscosity to entropy density ratio $η / s ≃ 0.24$ at the LHC.
Comments:
8 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1508.05878 [pdf]
25 citations

Affiliations

first authorsco-authorsvia INSPIRE