Nuclear Theory·nucl-th

Tuesday·April 26, 2016

12 papers—9 primary·3 cross-listed

01
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.
nucl-thPhys.Atom.Nucl.(2017)·9 citations
02
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.
nucl-thhep-ph
03
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.
nucl-thPRC(2017)·75 citations
04
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.
nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2016)·16 citations
05
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.
nucl-thPTEP(2016)·9 citations
06
$Ab$ $initio$ 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.
nucl-thPRC(2016)·53 citations
07
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.
nucl-thhep-phnucl-exPRC(2016)·41 citations
08
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.
nucl-thPRC(2016)·62 citations
09
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.
nucl-thnucl-exPRC(2017)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE