Nuclear Theory·nucl-th

Friday·July 6, 2018

8 papers—4 primary·4 cross-listed

01
[Submitted on 4 Jul 2018]
On the effect of high order empirical parameters on the nuclear equation of state
J. Margueron🇺🇸 · F. Gulminelli🇫🇷
A quantitative knowledge of the nuclear Equation of State (EoS) requires an accurate estimation of the uncertainties on the EoS parameters and their mutual correlations. Such correlations are empirically observed in a large set of EoS models by different authors, but they are not always fully understood. We show that some of these correlations can be interpreted from basic physical constraints imposed on a simple Taylor expansion of the binding energy around saturation density. In particular, we investigate the correlations among the following empirical parameters: the symmetry energy $E_{sy m}$ , the slope and curvature of the symmetry energy $L_{sy m}$ and $K_{sy m}$ , and the curvature and skewness of the binding energy in symmetric matter $K_{s a t}$ and $Q_{s a t}$ . The uncertainties on these correlations is estimated through analytical modelling as well as a meta-modelling analysis of the EoS subject to physical constraints. We show that a huge dispersion of the correlations among low order empirical parameters is induced by the unknown higher order empirical parameters, such as $K_{sy m}$ (second order) and $Q_{s a t}$ and $Q_{sy m}$ (third order). We also propose an explanation of the reason why $Q_{s a t}$ is weakly constrained by present experimental data. We conclude that selective observables on high order parameters, such as $K_{sy m}$ and $Q_{s a t}$ , should be better determined before the present uncertainties on the EoS can be further reduced.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1807.01729 [pdf]
PRC(2019)·59 citations
02
[Submitted on 5 Jul 2018]
Revisiting the isospin relaxation time in intermediate-energy heavy-ion collisions
Han-Sheng Wang · Jun Xu · Bao-An Li · Wen-Qing Shen
Isospin relaxation times characterizing isospin transport processes between the projectile and the target with different $N / Z$ ratios and that between the neck and the spectator with different isospin asymmetries and densities in intermediate-energy heavy-ion collisions are studied within an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model using the lattice Hamiltonian approach. The respective roles and time scales of the isospin diffusion and drift as the major mechanisms of isospin transport in intermediate-energy heavy-ion collisions are discussed. Effects of nuclear symmetry energy and neutron-proton effective mass splitting on the isospin relaxation times are examined.
Comments:
9 pages, 6 figures, minor modifications
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1807.01849 [pdf]
PRC(2018)·7 citations
03
[Submitted on 5 Jul 2018]
Heavy-ions collisions and fission dynamics with the time-dependent Hartree-Fock theory and its extensions
C. Simenel · A.S. Umar
Microscopic methods and tools to describe nuclear dynamics have considerably been improved in the past few years. They are based on the time-dependent Hartree-Fock (TDHF) theory and its extensions to include pairing correlations and quantum fluctuations. The TDHF theory is the lowest level of approximation of a range of methods to solve the quantum many-body problem, showing its universality to describe many-fermion dynamics at the mean-field level. The range of applications of TDHF to describe realistic systems allowing for detailed comparisons with experiment has considerably increased. For instance, TDHF is now commonly used to investigate fusion, multi-nucleon transfer and quasi-fission reactions. Thanks to the inclusion of pairing correlations, it has also recently led to breakthroughs in our description of the saddle to scission evolution, and, in particular, the non-adiabatic effects near scission. Beyond mean-field approaches such as the time-dependent random-phase approximation (TDRPA) and stochastic mean-field methods have reached the point where they can be used for realistic applications. We review recent progresses in both techniques and applications to heavy-ion collision and fission.
Comments:
Review article. 80 pages, 30 figures. Accepted for publication in Prog. Part. Nucl. Phys. Some typos corrected and references updated
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1807.01859 [pdf]
PPNP(2018)·180 citations
04
[Submitted on 5 Jul 2018]
Finite resonance widths influence the thermal-model description of hadron yields
Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇩🇪 · Horst Stoecker🇩🇪
Different scenarios for modeling resonances in a thermal model description of hadron yields measured in heavy-ion collisions are explored: the zero-width approximation, the energy independent Breit-Wigner scheme, and the energy dependent Breit-Wigner (eBW) scheme. Application of the eBW scheme leads to a notable suppression in the proton yields, stemming mainly from a reduced feeddown from $Δ$ resonances because of the threshold effects. A significantly improved agreement of thermal model with hadron yields measured in Pb-Pb collisions at $s_{_{N N}} = 2.76$ TeV by the ALICE collaboration is obtained in the eBW scheme at $T ≃ 155$ MeV, indicating a possible resolution of the so-called 'proton anomaly'. The results obtained show that there are significant systematic uncertainties in the thermal model due to the modeling of broad resonances.
Comments:
9 pages, 4 figures. Accepted for publication in Physical Review C, source code is available at https://github.com/vlvovch/1807.02079
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1807.02079 [pdf]
PRC(2018)·71 citations

Affiliations

first authorsco-authorsvia INSPIRE

On the effect of high order empirical parameters on the nuclear equation of state

Revisiting the isospin relaxation time in intermediate-energy heavy-ion collisions

Heavy-ions collisions and fission dynamics with the time-dependent Hartree-Fock theory and its extensions

Finite resonance widths influence the thermal-model description of hadron yields

Affiliations