Nuclear Theory·nucl-th

Tuesday·September 22, 2015

20 papers—13 primary·7 cross-listed

01
[Submitted on 18 Sept 2015]
Exact solutions of the Boltzmann equation and optimized hydrodynamic approaches for relativistic heavy-ion collisions
U. Heinz (Ohio State)🇺🇸 · D. Bazow (Ohio State)🇺🇸 · G.S. Denicol (McGill)🇨🇦 · M. Martinez (Ohio State)🇺🇸 · M. Nopoush (Kent State)🇺🇸 · J. Noronha (U. Sao Paulo)🇧🇷 · R. Ryblewski (Krakow)🇵🇱 · M. Strickland (Kent State)🇺🇸
Several recent results are reported from work aiming to improve the quantitative precision of relativistic viscous fluid dynamics for relativistic heavy-ion collisions. The dense matter created in such collisions expands in a highly anisotropic manner. Due to viscous effects this also renders the local momentum distribution anisotropic. Optimized hydrodynamic approaches account for these anisotropies already at leading order in a gradient expansion. Recently discovered exact solutions of the relativistic Boltzmann equation in anisotropically expanding systems provide a powerful testbed for such improved hydrodynamic approximations. We present the latest status of our quest for a formulation of relativistic viscous fluid dynamics that is optimized for applications to relativistic heavy-ion collisions.
Comments:
4 pages, 1 figure. Talk given at Hard Probes 2015. To appear in the proceedings
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1509.05818 [pdf]
Nucl.Part.Phys.Proc.(2016)·26 citations
02
[Submitted on 20 Sept 2015]
Surface Delta Interaction and g factors
Xiaofei Yu · Larry Zamick
Using an attractive surface delta interaction we obtain wave functions for 2 neutrons (or neutron holes) in the model space of 2 orbits (l=4, j=7/2) and (l=2, j=5/2). If we take the single particle energies to be degenerate we find that the g factors for I=2, 4 and 6 are all the same -namely the orbital g factor of the single nucleon. For a free neutron this quantity zero all 2particle or 2 hole g factors are equal to zero as well.. Only the orbital part of the g -factors contribute - the spin part cancels out. We then consider the effects of introducing a single energy splititng between the 2 orbits. We speculate that g factors for all n can be obtained by a linear approximation.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1509.05956 [pdf]
NPA(2016)·1 citation
03
[Submitted on 20 Sept 2015]
Enhancement factor for two-neutron transfer reactions with a schematic coupled-channels model
K. Hagino · G. Scamps
Probabilities for two-neutron transfer reactions, $P_{2n}$ , are often discussed in comparison with the square of the corresponding probabilities for one-neutron transfer process, $(P_{1n})^{2}$ , implicitly assuming that $(P_{1n})^{2}$ provides the probability of two-neutron transfer reactions in the absence of the pairing correlation. We use a schematic coupled-channels model, in which the transfers are treated as effective inelastic channels, and demonstrate that this model leads to $P_{2n} = (P_{1n})^{2} /4$ , rather than $P_{2n} = (P_{1n})^{2}$ , in the pure sequential limit. We argue that a simple model with spin-up and spin-down neutrons in a single-particle orbital also leads to the same conclusion.
Comments:
4 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1509.06012 [pdf]
PRC(2015)·8 citations
04
[Submitted on 20 Sept 2015]
Nuclear annihilation by antinucleons
Teck-Ghee Lee🇺🇸 · Cheuk-Yin Wong🇺🇸
We examine the momentum dependence of $p ˉ$ $p$ and $n ˉ$ $p$ annihilation cross sections by considering the transmission through a nuclear potential and the $p ˉ p$ Coulomb interaction. Compared to the $n ˉ p$ annihilation cross section, the $p ˉ p$ annihilation cross section is significantly enhanced by the Coulomb interaction for projectile momenta below $p_{lab} <$ 500 MeV/ $c$ , and the two annihilation cross sections approach the Pomeranchuk's equality limit [JETP Lett. {\bb 30}, 423 (1956)] at $p_{lab} \sim 500$ MeV/ $c$ . Using these elementary cross sections as the basic input data, the extended Glauber model is employed to evaluate the annihilation cross sections for $n ˉ$ and $p ˉ$ interaction with nuclei and the results compare well with experimental data.
Comments:
9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.06031 [pdf]
PRC(2016)·11 citations
05
[Submitted on 20 Sept 2015]
Estimating the relevance of predictions from nuclear mean-field models
P.-G. Reinhard
This contribution reviews the present status of the Skyrme-Hartree-Fock (SHF) approach as one of the leading self-consistent mean-field models in the physics of atomic nuclei. It starts with a brief summary of the formalism and strategy for proper calibration of the SHF functional. The main emphasis lies on an exploration of the reliability of predictions, particularly in the regime of extrapolations. Various strategies are discussed to explore the statistical and systematic errors of SHF. The strategies are illustrated on examples from actual applications. Variations of model and fit data are used to get an idea about systematic errors. The statistical error is evaluated in straightforward manner by statistical analysis based on $χ^{2}$ fits. This also allows also to evaluate the correlations (covariances) between observables which provides useful insights into the structure of the model and of the fitting strategy.
Comments:
manuscrtip submitted to Physica Scripta
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.06045 [pdf]
Phys.Scripta(2016)·18 citations
06
[Submitted on 20 Sept 2015]
Factorization of event-plane correlations over transverse momentum in relativistic heavy ion collisions in a multi-phase transport model
Kai Xiao · Feng Liu · Fuqiang Wang
Momentum-space azimuthal harmonic event planes (EP) are constructed from final-state midrapidity particles binned in transverse momentum (pT ) in sqrt(s_NN) = 200 GeV Au+Au collisions in a multi-phase transport (AMPT) model. The EP correlations between pT bins, corrected by EP resolutions, are smaller than unity. This indicates that the EP's decorrelate over pT in AMPT, qualitatively consistent with data and hydrodynamic calculations. It is further found that the EP correlations approximately factorize into single pT-bin EP correlations to a common plane. This common plane appears to be the momentum-space EP integrated over all pT, not the configuration space participant plane (PP).
Comments:
7 pages, 2 tables, 2 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1509.06070 [pdf]
PRC(2016)·8 citations
07
[Submitted on 21 Sept 2015]
Production of fragments and hyperfragments in antiproton-nucleus collisions
Zhao-Qing Feng🇨🇳
Formation mechanism of fragments with strangeness in collisions of antiprotons on nuclei has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport approach combined with a statistical model (GEMINI) for describing the decays of excited fragments. Production of strange particles in the antiproton induced nuclear reactions is modeled within the LQMD model, in which all possible reaction channels such as elastic scattering, annihilation, charge exchange and inelastic scattering in antibaryon-baryon, baryon-baryon and meson-baryon collisions have been included. A coalescence approach is developed for constructing hyperfragments in phase space after de-excitation of nucleonic fragments. The combined approach could describe the production of fragments in low-energy antiproton induced reactions. Hyperfragments are formed within the narrower rapidities and lower kinetic energies. It has advantage to produce heavier hyperfragments and hypernuclides with strangeness s=-2 (double- $Λ$ fragments) and s=1 ( $Λ$ -fragments) in antiproton induced reactions.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.06090 [pdf]
PRC(2016)·14 citations
08
[Submitted on 21 Sept 2015]
Chiral symmetry aspects in the open charm sector
Thomas Buchheim🇩🇪 · Thomas Hilger🇦🇹 · Burkhard Kampfer🇩🇪
QCD sum rules serve as tools to investigate changing hadronic properties in a hot and/or dense nuclear medium. The role of chiral symmetry breaking and restoration effects in a medium can be addressed also in the heavy-light meson sector. Thus, we consider Weinberg sum rules which refer to chiral partner mesons composed of a light and a heavy quark.
Comments:
Contribution to the SQM15 conference, Dubna, Russia. To appear in the proceedings
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1509.06144 [pdf]
J.Phys.Conf.Ser.(2016)·9 citations
09
[Submitted on 21 Sept 2015]
The $K^{-} p \to f_{1} (1285) Λ$ reaction within an effective Lagrangian approach
Ju-Jun Xie🇨🇳
The production of the $f_{1} (1285)$ resonance in the reaction of $K^{-} p \to f_{1} (1285) Λ$ is studied within an effective Lagrangian approach. The production process is described by the $t$ channel $K^{*+}$ meson exchange. My theoretical approach is based on the results of chiral unitary theory where the $f_{1} (1285)$ resonance is dynamically generated from the single channel $K ˉ K^{*} - c . c .$ interaction. The total and differential cross sections of the $K^{-} p \to f_{1} (1285) Λ$ reaction are evaluated. Within the coupling constant of the $f_{1} (1285)$ to $K ˉ K^{*}$ channel obtained from the chiral unitary theory and a cut off parameter $Λ_{c} \sim 1.5$ GeV in the form factors, the experimental measurement can be reproduced. This production process would provide further evidence for the $K ˉ K^{*} - c . c .$ nature of the $f_{1} (1285)$ state.
Comments:
Published on Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1509.06196 [pdf]
PRC(2015)·15 citations
10
[Submitted on 21 Sept 2015]
Relativistic three-nucleon calculations within the Bethe-Salpeter approach
S.G. Bondarenko · V.V. Burov · S.A. Yurev
The relativistic properties of the three-nucleon system are investigated using the Faddeev equations within the Bethe-Salpeter approach. The nucleon-nucleon interaction is chosen in a separable form. The Gauss quadrature method is used to calculate the integrals. The system of the integral equations are solving by iterations method. The binding energy and the partial-wave amplitudes (1S 0 and 3S 1) of the triton are found.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.06211 [pdf]
EPJ Web Conf.(2016)·4 citations
11
[Submitted on 21 Sept 2015]
Importance-Truncated Large-Scale Shell Model
Christina Stumpf · Jonas Braun · Robert Roth
We propose an importance-truncation scheme for the large-scale nuclear shell model that extends its range of applicability to larger valence spaces and mid-shell nuclei. It is based on a perturbative measure for the importance of individual basis states that acts as an additional truncation for the many-body model space in which the eigenvalue problem of the Hamiltonian is solved numerically. Through a posteriori extrapolations of all observables to vanishing importance threshold, the full shell-model results can be recovered. In addition to simple threshold extrapolations, we explore extrapolations based on the energy variance. We apply the importance-truncated shell model for the study of 56-Ni in the pf valence space and of 60-Zn and 64-Ge in the pfg9/2 space. We demonstrate the efficiency and accuracy of the approach, which pave the way for future shell-model calculations in larger valence spaces with valence-space interactions derived in ab initio approaches.
Comments:
5 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.06239 [pdf]
PRC(2016)·36 citations
12
[Submitted on 21 Sept 2015]
Toward a simultaneous description of $R_{AA}$ and $v_{2}$ for heavy quarks
Santosh K. Das🇮🇹 · Francesco Scardina🇮🇹 · Salvatore Plumari🇮🇹 · Vincenzo Greco🇮🇹
The two key observables related to heavy quarks that have been measured in RHIC and LHC energies are the nuclear suppression factor $R_{AA}$ and the elliptic flow $v_{2}$ . Simultaneous description of these two observables is a top challenge for all the existing models. We have highlighted how a consistent combination of four ingredients i.e the temperature dependence of the energy loss, full solution of the Boltzmann collision integral for the momentum evolution of heavy quark, hadronization by coalescence, then the hadronic rescattering, responsible to address a large part of such a puzzle. We have considered four different models to evaluate the temperature dependence of drag coefficients of the heavy quark in QGP. All these four different models are set to reproduce the same $R_{AA}$ as of the experiments. We have shown that for the same $R_{AA}$ , the $v_{2}$ could be quite different depending on the interaction dynamics as well as other ingredients.
Comments:
4 pages, To appear in the proceedings of SQM-2015
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1509.06307 [pdf]
J.Phys.Conf.Ser.(2016)·5 citations
13
[Submitted on 21 Sept 2015]
Hyperon puzzle and the RMF model with scaled hadron masses and coupling constants
E.E. Kolomeitsev🇸🇰 · K.A. Maslov🇷🇺 · D.N. Voskresensky🇷🇺
The equation of state of cold baryonic matter is studied within a relativistic mean-field model with hadron masses and coupling constants depending on a scalar field. We demonstrate that if the effective nucleon mass stops to decrease with a density increase at densities $n > n_{*} > n_{0}$ , where $n_{0}$ is the nuclear saturation density, the equation of state stiffens for these densities and the limiting neutron star mass increases. The stabilization of the nucleon mass can be realised if in the equation of motion for the scalar mean-field there appear a term sharply varying in a narrow vicinity of the field value corresponding to the density $n_{*}$ . We show several possible realizations of this mechanism getting sufficiently stiff equations of state. The appearance of hyperons in dense neutron star interiors is accounted for. The obtained equations of state remain sufficiently stiff if the reduction of the $ϕ$ meson mass is incorporated. Thereby, the hyperon puzzle can be resolved.
Comments:
6 pages, 3 figures; Proceedings of the Strangeness in Quark Matter 2015, Dubna, July 6-11, 2015
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1509.06312 [pdf]
J.Phys.Conf.Ser.(2016)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE