Nuclear Theory·nucl-th

Tuesday·March 6, 2018

12 papers—10 primary·2 cross-listed

01
[Submitted on 2 Mar 2018]
The temperature dependence of the shell corrections
F.A. Ivanyuk · C. Ishizuka · M.D. Usang · S. Chiba
We have examined the dependence of the shell correction to the nuclear liquid drop energy at finite excitations on the excitation energy (temperature). For this we have calculated the shell correction to the energy and free energy in very broad region of nuclei and deformations starting directly from their formal definitions. We have found out that the dependence of the shell corrections on the excitation energy differ substantially from the widely used approximation $δ E (E^{*}) = δ E (0) exp (- E^{*} / E_{d})$ both at small and large excitations. In particular, below the critical temperature at which the pairing effects vanish, the shell correction to the free energy is rather insensitive to the excitation energy. We suggest a more accurate approximation for the temperature dependence of the shell correction to the energy and free energy that is expressed in terms of the shell correction to the energy of independent particles and the shell correction to the pairing energy at T=0 and few fitted constants.
Comments:
10 pages, 13 figures, accepted for publication in PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01036 [pdf]
PRC(2018)·41 citations
02
[Submitted on 4 Mar 2018]
Reply to Comment on "Solution of the Specific Model of Five-body Problem to Investigate the Effective Alpha-Nucleon Interaction in a Partial-Wave analysis"
E. Ahmadi Pouya · A. A. Rajabi
The present paper is written in response to the comment of M. R. Hadizadeh et. al on our original paper "Solution of the Specific Model of Five-body Problem to Investigate the Effective Alpha-Nucleon Interaction in a Partial-Wave analysis" [Acta Physica Polonica B, 48, 1279 (2017)]. In this paper we present our clarifications and statements on the authors of the comment arguments about of the accuracy of the procedure in solution of simple five- and four-body problems. In this regard our arguments turn out to be very efficient mainly discussed from the authors misunderstanding of the issues discussed in the original paper. In fact, the authors of the comment aims to exaggeratedly show that our paper is entirely incorrect, but our following statements prove that the authors of the comment statements are inimical and often inconsequential.
Comments:
9 page, 2 figures, comment
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01322 [pdf]
03
[Submitted on 4 Mar 2018]
The radius of a typical-mass neutron star and chiral effective field theory
Francesca Sammarruca · Randy Millerson
We calculate neutron star masses and radii from equations of state based on recent high-quality chiral nucleon-nucleon potentials up to fifth order of the chiral expansion and the leading chiral three- nucleon force. Our focus is on the radius of a 1.4 M_{Sun} neutron star, for which we report predictions that are consistent with the most recent constraints. We also show the full M(R) relations up to their respective maximum masses. Beyond the densities for which microscopic predictions are derived from chiral forces, the equations of state are obtained via polytropic continuations. However, the radius of a 1.4 M_{Sun} neutron star is nearly insensitive to the high-density extrapolation.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01437 [pdf]
J.Phys.(2019)·9 citations
04
[Submitted on 4 Mar 2018]
An Investigation of the Bound State Solutions of the Klein-Gordon Equation for the Generalized Woods-Saxon Potential in Spin Symmetry and Pseudo-spin Symmetry Limits
Bekir Can Lütfüoğlu🇹🇷
Recently, scattering of a Klein-Gordon particle in the presence of mixed scalar-vector generalized symmetric Woods-Saxon potential was investigated for the spin symmetric and the pseudo-spin symmetric limits in one spatial dimension. In this manuscript, the bound state solutions of the Klein-Gordon equation with mixed scalar-vector generalized symmetric Woods-Saxon potential are examined analytically within the framework of spin and pseudo-spin symmetry limits. We prove that the occurrence of bound state energy spectrum exists only in the spin symmetric limit, while in the pseudo-spin symmetric limit, the bound state spectrum does not exist. Besides the theoretical proof, the Newton-Raphson numerical methods are used to calculate the bound state energy spectra of a neutral Kaon particle, confined in a generalized symmetric Woods-Saxon potential, energy well constituted with repulsive or attractive surface interactions, for the spin and pseudo-spin symmetric limits, respectively. Numerical results are consistent with the non-existence of the bound state energy spectrum in the pseudo-spin symmetric limit.
Comments:
20 pages, 10 Figures, 2 Tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01439 [pdf]
Eur.Phys.J.Plus(2018)·13 citations
05
[Submitted on 5 Mar 2018]
Vortex rings in fragmentation regions in heavy-ion collisions at $s_{N N} =$ 39 GeV
Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺
Vorticity generated in heavy-ion collisions at energy of $s_{N N} =$ 39 GeV is studied. Simulations are performed within a model of the three-fluid dynamics. A peculiar structure consisting of two vortex rings is found: one ring in the target fragmentation region and another one in the projectile fragmentation region. These rings are also formed in central collisions. The matter rotation is opposite in this two rings. These vortex rings are already formed at the early stage of the collision together with primordial fragmentation regions. The average vorticity, responsible for the global polarization of the observed $Λ$ and $Λ ˉ$ , is also studied. In the semi-central collisions the average vorticity in the midrapidity region turns out to be more than an order of magnitude lower than the total one. The total vorticity is dominated by the contributions of the fragmentation regions and is produced because of asymmetry of the vortex rings in noncentral collisions. This suggests that in semi-central collisions the global polarization in the fragmentation regions should be at least an order of magnitude higher than that observed by the STAR collaboration in the midrapidity. This polarization should be asymmetrical in the reaction plain and correlate with the corresponding directed flow.
Comments:
10 pages, 7 figures, version published in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.01525 [pdf]
PRC(2018)·30 citations
06
[Submitted on 5 Mar 2018]
Impact of Fission Neutron Energies on Reactor Antineutrino Spectra
B. R. Littlejohn🇺🇸 · A. Conant🇺🇸 · D. A. Dwyer🇺🇸 · A. Erickson🇺🇸 · I. Gustafson🇺🇸 · K. Hermanek🇺🇸
Recent measurements of reactor-produced antineutrino fluxes and energy spectra are inconsistent with models based on measured thermal fission beta spectra. In this paper, we examine the dependence of antineutrino production on fission neutron energy. In particular, the variation of fission product yields with neutron energy has been considered as a possible source of the discrepancies between antineutrino observations and models. In simulations of low-enriched and highly-enriched reactor core designs, we find a substantial fraction of fissions (from 5% to more than 40%) are caused by non-thermal neutrons. Using tabulated evaluations of nuclear fission and decay, we estimate the variation in antineutrino emission by the prominent fission parents U-235, Pu-239, and Pu-241 versus neutron energy. The differences in fission neutron energy are found to produce less than 1% variation in detected antineutrino rate per fission of U-235, Pu-239, and Pu-241. Corresponding variations in the antineutrino spectrum are found to be less than 10% below 7 MeV antineutrino energy, smaller than current model uncertainties. We conclude that insufficient modeling of fission neutron energy is unlikely to be the cause of the various reactor anomalies. Our results also suggest that comparisons of antineutrino measurements at low-enriched and highly-enriched reactors can safely neglect the differences in the distributions of their fission neutron energies.
Comments:
10 pages, 5 figures, 4 tables. Submitted to PRD
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01787 [pdf]
PRD(2018)·22 citations
07
[Submitted on 5 Mar 2018]
(3+1)-dimensional anisotropic fluid dynamics with a lattice QCD equation of state
M. McNelis🇺🇸 · D. Bazow🇺🇸 · U. Heinz🇺🇸
Anisotropic hydrodynamics improves upon standard dissipative fluid dynamics by treating certain large dissipative corrections non-perturbatively. Relativistic heavy-ion collisions feature two such large dissipative effects: (i) Strongly anisotropic expansion generates a large shear stress component which manifests itself in very different longitudinal and transverse pressures, especially at early times. (ii) Critical fluctuations near the quark-hadron phase transition lead to a large bulk viscous pressure on the conversion surface between hydrodynamics and a microscopic hadronic cascade description of the final collision stage. We present a new dissipative hydrodynamic formulation for non-conformal fluids where both of these effects are treated nonperturbatively. The evolution equations are derived from the Boltzmann equation in the 14-moment approximation, using an expansion around an anisotropic leading-order distribution function with two momentum-space deformation parameters, accounting for the longitudinal and transverse pressures. To obtain their evolution we impose generalized Landau matching conditions for the longitudinal and transverse pressures. We describe an approximate anisotropic equation of state that relates the anisotropy parameters with the macroscopic pressures. Residual shear stresses are smaller and are treated perturbatively, as in standard second-order dissipative fluid dynamics. The resulting optimized viscous anisotropic hydrodynamic evolution equations are derived in 3+1 dimensions and tested in a (0+1)-dimensional Bjorken expansion, using a state-of-the-art lattice equation of state. Comparisons with other viscous hydrodynamical frameworks are presented.
Comments:
27 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.01810 [pdf]
PRC(2018)·34 citations
08
[Submitted on 5 Mar 2018]
Centrality fluctuations in heavy-ion collisions
Mingliang Zhou🇺🇸 · Jiangyong Jia🇺🇸
Volume or centrality fluctuations (CF) is one of the main uncertainties for interpreting the centrality dependence of many experimental observables. The CF is constrained by centrality selection based on particle multiplicity in a reference subevent, and contributes to observables measured in another subevent. Using a Glauber-based independent source model, we study the influence of CF on several distributions of multiplicity $N$ and eccentricities $ϵ_{n}$ : $p (N)$ , $p (ϵ_{n})$ , $p (ϵ_{n}, ϵ_{m})$ and $p (N, ϵ_{n})$ , where the effects of CF is quantified using multi-particle cumulants of these distributions. In mid-central collisions, a general relation is established between the multiplicity fluctuation and resulting CF in the reference subevent. In ultra-central collisions, where distribution of particle production sources is strongly distorted, we find these cumulants exhibit rich sign-change patterns, due to observable-dependent non-Gaussianity in the underlying distributions. The details of sign-change pattern change with the size of the collision systems. Simultaneous comparison of these different types cumulants between model prediction and experimental data can be used to constrain the CF and particle production mechanism in heavy-ion collisions. Since the concept of centrality and CF are expected to fluctuate in the longitudinal direction within a single event, we propose to use pseudorapidity-separated subevent cumulant method to explore the nature of intra-event fluctuations of centrality and collective dynamics. The subevent method can be applied for any bulk observable that is sensitive to centrality, and has the potential to separate different mechanisms for multiplicity and flow fluctuations happening at different time scales. The forward detector upgrades at RHIC and LHC will greatly enhance such studies in the future.
Comments:
26 pages and 21 figures, replace with published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1803.01812 [pdf]
PRC(2018)·48 citations
09
[Submitted on 5 Mar 2018]
Optical model potential analysis of $n ˉ A$ and $n A$ interactions
Teck-Ghee Lee🇺🇸 · Cheuk-Yin Wong🇺🇸
We use a momentum-dependent optical model potential to analyze the annihilation cross sections of antineutron $n ˉ$ on C, Al, Fe, Cu, Ag, Sn, and Pb nuclei for projectile momenta $p_{lab}$ $≲$ 500 MeV/ $c$ . We obtain good description of annihilation cross sections data of Barbina {\it et al.} [Nucl.~Phys.~A {\bf 612}, ~346~(1997)] and of Astrua {\it et al.} [Nucl.~Phys.~A {\bf 697},~209~(2002)] which exhibit an interesting dependence of the cross sections on the $p_{lab}$ as well as on the target atomic mass number $A$ . We also obtain the neutron ( $n$ ) non-elastic reaction cross sections for the same targets. Contrasting the $n A$ reaction cross sections $σ_{rec}^{n A}$ to the $n ˉ A$ annihilation cross sections $σ_{ann}^{n ˉ A}$ , we find the $σ_{ann}^{n ˉ A}$ is significantly larger than the $σ_{rec}^{n A}$ , that is, the $σ_{ann}^{n ˉ A}$ / $σ_{rec}^{n A}$ cross section ratio lies between the values of order 1.8 and 3.8 in the momentum region where comparison is possible. The dependence of the annihilation cross section on the projectile charge is also examined in comparison with antiproton $p ˉ$ . Here we predict the $p ˉ A$ annihilation cross section on the simplest assumption that both $p ˉ A$ and $n ˉ A$ interactions have the same nuclear part of the optical model potential but differs only on the electrostatic Coulomb interaction. Deviation from such simple model extrapolation in measurements will provide new information on the difference between $n ˉ A$ and $p ˉ A$ potentials.
Comments:
15 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.01820 [pdf]
PRC(2018)·16 citations
10
[Submitted on 5 Mar 2018]
Phases of dense matter in compact stars
David Blaschke🇵🇱 · Nicolas Chamel🇧🇪
Formed in the aftermath of gravitational core-collapse supernova explosions, neutron stars are unique cosmic laboratories for probing the properties of matter under extreme conditions that cannot be reproduced in terrestrial laboratories. The interior of a neutron star, endowed with the highest magnetic fields known and with densities spanning about ten orders of magnitude from the surface to the centre, is predicted to exhibit various phases of dense strongly interacting matter, whose physics is reviewed in this chapter. The outer layers of a neutron star consist of a solid nuclear crust, permeated by a neutron ocean in its densest region, possibly on top of a nuclear "pasta" mantle. The properties of these layers and of the homogeneous isospin asymmetric nuclear matter beneath constituting the outer core may still be constrained by terrestrial experiments. The inner core of highly degenerate, strongly interacting matter poses a few puzzles and questions which are reviewed here together with perspectives for their resolution. Consequences of the dense-matter phases for observables such the neutron-star mass-radius relationship and the prospects to uncover their structure with modern observational programmes are touched upon.
Comments:
62 pages, 11 figures, revised and extended contribution to the White Book of "NewCompStar" European COST Action MP1304. arXiv admin note: text overlap with arXiv:1707.04966 by other authors
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.01836 [pdf]
Astrophys.Space Sci.Libr.(2018)·93 citations

Affiliations

first authorsco-authorsvia INSPIRE