Nuclear Theory·nucl-th

Tuesday·April 26, 2016

12 papers—9 primary·3 cross-listed

01
[Submitted on 23 Apr 2016]
Semiclassical approaches to nuclear dynamics
A.G. Magner🇺🇦 · D.V. Gorpinchenko🇺🇦 · J. Bartel🇫🇷
The extended Gutzwiller trajectory approach is presented for the semiclassical description of nuclear collective dynamics, in line with the main topics of the fruitful activity of V.G. Solovjov. Within the Fermi-liquid droplet model, the leptodermous effective surface approximation was applied to calculations of energies, sum rules and transition densities for the neutron-proton asymmetry of the isovector giant-dipole resonance and found to be in good agreement with the experimental data. By using the Strutinsky shell correction method, the semiclassical collective transport coefficients such as nuclear inertia, friction, stiffness, and moments of inertia can be derived beyond the quantum perturbation approximation of the response function theory and the cranking model.The averaged particle-number dependence of the low-lying collective vibrational states are described in good agreement with basic experimental data, mainly due to an enhancement of the collective inertia as compared to its irrotational flow value. Shell components of the moment of inertia are derived in terms of the periodic-orbit free-energy shell corrections. A good agreement between the semiclassical extended Thomas-Fermi moments of inertia with shell corrections and the quantum results is obtained for different nuclear deformations and particle numbers. Shell effects are shown to be exponentially dampted out with increasing temperature in all the transport coefficients.
Comments:
83 pages, 39 figures, 4 tables, corrected typos and improved English
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1604.06866 [pdf]
Phys.Atom.Nucl.(2017)·9 citations
02
[Submitted on 23 Apr 2016]
The Role of Vector Mesons for Emergent Scale-Chiral Symmetry in Nuclear Interactions
Won-Gi Paeng · Mannque Rho
When a light scalar dilaton $σ$ and the light-quark vector mesons $V = (ρ, ω)$ are incorporated into an effective scale-invariant hidden local symmetric (sHLS) Lagrangian, scale symmetry for $σ$ and local gauge symmetry for $V$ , both invisible in QCD in the vacuum, arise as emergent symmetries at a density above $n_{1/2} \sim 2 n_{0}$ , a phenomenon highly relevant for massive compact stars, hitherto unobserved in standard chiral pertubative approaches. What takes place involves a topology change at $n_{1/2}$ , and as the density increases beyond, (1) exposes a parity doubling in the nucleon structure, (2) triggers drastic change in the nuclear tensor force and (3) stiffens the nuclear symmetry energy as density exceeds $n_{1/2}$ . It results from an intricate interplay between the two hidden symmetries that the $ρ$ meson moves toward the vector manifestation (VM) fixed point where $m_{ρ} \to 0$ and the velocity of sound $v_{s}$ in the dense matter approaches the conformal symmetry value $v_{s} / c = 1/3$ , indicating a presence of an infrared fixed point at which the dilaton mass vanishes.
Comments:
revised for publication and replaced by arXiv:1611.09975
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1604.06889 [pdf]
03
[Submitted on 24 Apr 2016]
Self-consistent relativistic quasiparticle random-phase approximation and its applications to charge-exchange excitations and $β$ -decay half-lives
Z. M. Niu · Y. F. Niu · H. Z. Liang · W. H. Long · J. Meng
The self-consistent quasiparticle random-phase approximation (QRPA) approach is formulated in the canonical single-nucleon basis of the relativistic Hatree-Fock-Bogoliubov (RHFB) theory. This approach is applied to study the isobaric analog states (IAS) and Gamov-Teller resonances (GTR) by taking Sn isotopes as examples. It is found that self-consistent treatment of the particle-particle residual interaction is essential to concentrate the IAS in a single peak for open-shell nuclei and the Coulomb exchange term is very important to predict the IAS energies. For the GTR, the isovector pairing can increase the calculated GTR energy, while the isoscalar pairing has an important influence on the low-lying tail of the GT transition. Furthermore, the QRPA approach is employed to predict nuclear $β$ -decay half-lives. With an isospin-dependent pairing interaction in the isoscalar channel, the RHFB+QRPA approach almost completely reproduces the experimental $β$ -decay half-lives for nuclei up to the Sn isotopes with half-lives smaller than one second. Large discrepancies are found for the Ni, Zn, and Ge isotopes with neutron number smaller than $50$ , as well as the Sn isotopes with neutron number smaller than $82$ . The potential reasons for these discrepancies are discussed in detail.
Comments:
34 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1604.07011 [pdf]
PRC(2017)·75 citations
04
[Submitted on 24 Apr 2016]
Dilepton production with the SMASH model
Janus Weil🇩🇪 · Jan Staudenmaier🇩🇪 · Hannah Petersen🇩🇪
In this work the SMASH model is presented ("Simulating Many Accelerated Strongly-Interacting Hadrons"), a next-generation hadronic transport approach, which is designed to describe the non-equilibrium evolution of hadronic matter in heavy-ion collisions. We discuss first dilepton spectra obtained with SMASH in the few-GeV energy range of GSI/FAIR, where the dynamics of hadronic matter is dominated by the production and decay of various resonance states. In particular we show how electromagnetic transition form factors can emerge in a transport picture under the hypothesis of vector-meson dominance.
Comments:
5 pages, 3 figures, proceedings of FAIRNESS 2016
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1604.07028 [pdf]
J.Phys.Conf.Ser.(2016)·16 citations
05
[Submitted on 25 Apr 2016]
Isospin Projected Antisymmetrized Molecular Dynamics and its Application to $^{10}$ B
Hiroyuki Morita · Yoshiko Kanada-En'yo
To investigate $p n$ pair correlations in $N = Z = odd$ nuclei, we develop a new framework based on the generator coordinate method of the $β γ$ constraint antisymmetrized molecular dynamics. In the framework, the isospin projection is performed before the energy variation to obtain the wave function optimized for each isospin. We apply the method to $^{10} B$ and show that it works well to describe coexistence of $T = 0$ and $T = 1$ states in low-energy spectra. Structures of low-lying states and $p n$ correlations are investigated. Strong $M 1$ ( $0_{1}^{+} \to 1_{1}^{+}$ ) and $E 2$ ( $1_{1}^{+} \to 1_{2}^{+}$ ) transitions are understood by the spin excitation of the $p n$ pair and the rotation of a deformed core, respectively.
Comments:
19 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1604.07131 [pdf]
PTEP(2016)·9 citations
06
[Submitted on 25 Apr 2016]
$Ab$ $initio$ nuclear many-body perturbation calculations in the Hartree-Fock basis
Baishan Hu · Furong Xu · Zhonghao Sun · James P. Vary · Tong Li
Starting from realistic nuclear forces, the chiral N $^{3}$ LO and JISP16, we have applied many-body perturbation theory (MBPT) to the structure of closed-shell nuclei, $^{4}$ He and $^{16}$ O. The two-body N $^{3}$ LO interaction is softened by a similarity renormalization group transformation while JISP16 is adopted without renormalization. The MBPT calculations are performed within the Hartree-Fock (HF) bases. The angular momentum coupled scheme is used, which can reduce the computational task. Corrections up to the third order in energy and up to the second order in radius are evaluated. Higher-order corrections in the HF basis are small relative to the leading-order perturbative result. Using the anti-symmetrized Goldstone diagram expansions of the wave function, we directly correct the one-body density for the calculation of the radius, rather than calculate corrections to the occupation propabilities of single-particle orbits as found in other treatments. We compare our results with other methods where available and find good agreement. This supports the conclusion that our methods produce reasonably converged results with these interactions. We also compare our results with experimental data.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1604.07146 [pdf]
PRC(2016)·53 citations
07
[Submitted on 25 Apr 2016]
Non-Gaussian eccentricity fluctuations
Hanna Grönqvist🇫🇷 · Jean-Paul Blaizot🇫🇷 · Jean-Yves Ollitrault🇫🇷
We study the fluctuations of the anisotropy of the energy density profile created in a high-energy collision at the LHC. We show that the anisotropy in harmonic $n$ has generic non-Gaussian fluctuations. We argue that these non-Gaussianities have a universal character for small systems such as p+Pb collisions, but not for large systems such as Pb+Pb collisions where they depend on the underlying non-Gaussian statistics of the initial density profile. We generalize expressions for the eccentricity cumulants $ε_{2} {4}$ and $ε_{3} {4}$ previously obtained within the independent-source model to a general fluctuating initial density profile.
Comments:
14 pages. Minor revision
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1604.07230 [pdf]
PRC(2016)·41 citations
08
[Submitted on 25 Apr 2016]
Covariant energy density functionals: nuclear matter constraints and global ground state properties
A. V. Afanasjev · S. E. Agbemava
The correlations between global description of the ground state properties (binding energies, charge radii) and nuclear matter properties of the state-of-the-art covariant energy density functionals have been studied. It was concluded that the strict enforcement of the constraints on the nuclear matter properties (NMP) defined in Ref.\ \cite{RMF-nm} will not necessary lead to the functionals with good description of the binding energies and other ground and excited state properties. In addition, it will not substantially reduce the uncertainties in the predictions of the binding energies in neutron-rich systems. It turns out that the functionals, which come close to satisfying these NMP constraints, have some problems in the description of existing data. On the other hand, these problems are either absent or much smaller in the functionals which are carefully fitted to finite nuclei but which violate some NMP constraints. This is a consequence of the fact that the properties of finite nuclei are defined not only by nuclear matter properties but also by underlying shell effects. The mismatch of phenomenological content, existing in all modern functionals, related to nuclear matter physics and the physics of finite nuclei could also be responsible.
Comments:
14 pages, 9 figures, Physical Review C, in press
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1604.07296 [pdf]
PRC(2016)·62 citations
09
[Submitted on 25 Apr 2016]
Origin of the mass splitting of azimuthal anisotropies in a multi-phase transport model
Hanlin Li🇨🇳 · Liang He🇺🇸 · Zi-Wei Lin🇺🇸 · Denes Molnar🇺🇸 · Fuqiang Wang🇺🇸 · Wei Xie🇺🇸
Both hydrodynamics-based models and a multi-phase transport (AMPT) model can reproduce the mass splitting of azimuthal anisotropy ( $v_{n}$ ) at low transverse momentum ( $p_{⊥}$ ) as observed in heavy ion collisions. In the AMPT model, however, $v_{n}$ is mainly generated by the parton escape mechanism, not by the hydrodynamic flow. In this study we provide detailed results on the mass splitting of $v_{n}$ in this transport model, including $v_{2}$ and $v_{3}$ of various hadron species in d+Au and Au+Au collisions at the Relativistic Heavy Ion Collider and p+Pb collisions at the Large Hadron Collider. We show that the mass splitting of hadron $v_{2}$ and $v_{3}$ in AMPT first arises from the kinematics in the quark coalescence hadronization process, and then, more dominantly, comes from hadronic rescatterings, even though the contribution from the latter to the overall charged hadron $v_{n}$ is small. We further show that there is no qualitative difference between heavy ion collisions and small-system collisions or between elliptic ( $v_{2}$ ) and triangular ( $v_{3}$ ) anisotropies. Our studies thus demonstrate that the mass splitting of $v_{2}$ and $v_{3}$ at low- $p_{⊥}$ is not a unique signature of hydrodynamic collective flow but can be the interplay of several physics effects.
Comments:
11 pages, 12 figures. Followup long paper to H. Li et al. Phys. Rev. C 93 (2016) 051901(R) (2016) [arXiv:1601.05390]; changes from v1 to v2: added phi-meson results in Fig.2 and Fig.11; v3: published version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1604.07387 [pdf]
PRC(2017)·34 citations
10
[Submitted on 23 Apr 2016] (cross-list from cond-mat.stat-mech)
q-Gamow States for intermediate energies
A. Plastino · M. C. Rocca · D. J. Zamora
In a recent paper [Nuc. Phys. A {\bf 948}, (2016) 19] we have demonstrated the possible existence of Tsallis' q-Gamow states. Now, accelerators' experimental evidence for Tsallis' distributions has been ascertained only at very high energies. Here, instead, we develop a different set of q-Gamow states for which the associated q-Breit-Wigner distribution could easily be found at intermediate energies, for which accelerators are available at many locations. In this context, it should be strongly emphasized [Physica A {\bf 388} (2009) 601] that, empirically, one never exactly and unambiguously "detects" pure Gaussians, but rather q-Gaussians. A prediction is made via Eq.(3.30)
Comments:
14 pages, no figures
Subjects:
Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1604.06910 [pdf]
NPA(2016)·4 citations
11
[Submitted on 25 Apr 2016] (cross-list from hep-ph)
Kondo phase diagram of quark matter
Shigehiro Yasui🇯🇵 · Kei Suzuki🇯🇵 · Kazunori Itakura🇯🇵
We discuss the ground state of a quark matter containing heavy quarks as impurities in a simple model which exhibits the QCD Kondo effect. The model includes a current-current interaction with the color exchange between a light quark ( $ψ$ ) and a heavy quark ( $Ψ$ ). We introduce a gap function $Δ \sim ⟨ ψ ˉ Ψ ⟩$ which represents the correlation between $ψ$ and $Ψ$ , and perform the mean-field approximation assuming that heavy quarks are uniformly distributed. Values of the gap $Δ$ measure the strength of mixing between $ψ$ and $Ψ$ . The gap equation obtained from the minimum of the thermodynamical potential together with the condition for the heavy-quark number conservation turns out to allow for nonzero values of the gap as the most stable state. We draw a phase diagram in $μ$ (the light-quark chemical potential) and $λ$ (an analog of the heavy-quark chemical potential) plane, and identify the region where the QCD Kondo effect occurs.
Comments:
13 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
1604.07208 [pdf]
NPA(2019)·34 citations
12
[Submitted on 25 Apr 2016] (cross-list from hep-ph)
Excitation functions of parameters in Erlang distribution, Schwinger mechanism, and Tsallis statistics in RHIC BES program
Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸
Experimental results of the transverse momentum distributions of phi mesons and $Ω$ hyperons produced in gold-gold (Au-Au) collisions with different centrality intervals, measured by the STAR Collaboration at different energies (7.7, 11.5, 19.6, 27, and 39 GeV) in the beam energy scan (BES) program at the relativistic heavy ion collider (RHIC), are approximately described by the single Erlang distribution and the two-component Schwinger mechanism. Meanwhile, the STAR experimental transverse momentum distributions of negatively charged particles, produced in Au-Au collisions at RHIC BES energies, are approximately described by the two-component Erlang distribution and the single Tsallis statistics. The excitation functions of free parameters are obtained from the fit to the experimental data. A weak softest point in the string tension in $Ω$ hyperon spectra is observed at 7.7 GeV.
Comments:
18 pages, 7 figures, The European Physical Journal A, accepted
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1604.07218 [pdf]
EPJA(2016)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE