Nuclear Theory·nucl-th

Tuesday·January 20, 2015

13 papers—9 primary·4 cross-listed

01
Nuclear energy density functionals: what we can learn about/from their global performance?
A. V. Afanasjev · S. E. Agbemava · D. Ray · P. Ring
A short review of recent results on the global performance of covariant energy density functionals is presented. It is focused on the analysis of the accuracy of the description of physical observables of ground and excited states as well as to related theoretical uncertainties. In addition, a global analysis of pairing properties is presented and the impact of pairing on the position of two-neutron drip line is discussed.
nucl-thAIP Conf.Proc.(2015)·0 citations
02
The neutron drip line: single-particle degrees of freedom and pairing properties as sources of theoretical uncertainties
A. V. Afanasjev · S. E. Agbemava · D. Ray · P. Ring
The sources of theoretical uncertainties in the prediction of the two-neutron drip line are analyzed in the framework of covariant density functional theory. We concentrate on single-particle and pairing properties as potential sources of these uncertainties. The major source of these uncertainties can be traced back to the differences in the underlying single-particle structure of the various covariant energy density functionals (CEDF). It is found that the uncertainties in the description of single-particle energies at the two-neutron drip line are dominated by those existing already in known nuclei. Only approximately one third of these uncertainties are due to the uncertainties in the isovector channel of CEDF's. Thus, improving the CEDF description of single-particle energies in known nuclei will also reduce the uncertainties in the prediction of the position of two-neutron drip line. The predictions of pairing properties in neutron rich nuclei depend on the CEDF. Although pairing properties affect moderately the position of the two-neutron drip line they represent only a secondary source for the uncertainties in the definition of the position of the two-neutron drip line.
nucl-thPRC(2015)·76 citations
03
Competition between Coulomb and Symmetry Potential in Semi-peripheral Heavy-ion Collisions
Qianghua Wu🇨🇳 · Yingxun Zhang🇨🇳 · Zhigang Xiao🇨🇳 · Rensheng Wang🇨🇳 · Yang Zhang🇨🇳 · Zhuxia Li🇨🇳 · Ning Wang🇨🇳 · R.H.Schowalter🇺🇸
The anisotropy of angular distributions of emitted nucleons and light charged particles for the asymmetric reaction system, $^{40}$ Ar+ $^{197}$ Au, at b=6fm and $E_{b e am}$ =35, 50 and 100MeV/u, are investigated by using the Improved Quantum Molecular Dynamics model. The competition between the symmetry potential and Coulomb potential shows large impacts on the nucleons and light charged particles emission in projectile and target region. As a result of this competition, the angular distribution anisotropy of coalescence invariant Y(n)/Y(p) ratio at forward regions shows sensitivity to the stiffness of symmetry energy as well as the value of Y(n)/Y(p). This observable can be further checked against experimental data to understand the reaction mechanism and to extract information about the symmetry energy at subsaturation densities.
nucl-thnucl-exPRC(2015)·14 citations
04
Parity violation in quasielastic electron-nucleus scattering within the relativistic impulse approximation
R. González-Jiménez🇪🇸 · J. A. Caballero🇪🇸 · T. W. Donnelly🇺🇸
We study parity violation in quasielastic (QE) electron-nucleus scattering using the relativistic impulse approximation. Different fully relativistic approaches have been considered to estimate the effects associated with the final-state interactions. We have computed the parity-violating quasielastic (PVQE) asymmetry and have analyzed its sensitivity to the different ingredients that enter in the description of the reaction mechanism: final-state interactions, nucleon off-shellness effects, current gauge ambiguities. Particular attention has been paid to the description of the weak neutral current form factors. The PVQE asymmetry is proven to be an excellent observable when the goal is to get precise information on the axial-vector sector of the weak neutral current. Specifically, from measurements of the asymmetry at backward scattering angles good knowledge of the radiative corrections entering in the isovector axial-vector sector can be gained. Finally, scaling properties shown by the interference $γ - Z$ nuclear responses are also analyzed.
nucl-thPRC(2015)·4 citations
05
Parity violation and dynamical relativistic effects in $(e, e^{'} N)$ reactions
R. González-Jiménez🇪🇸 · J. A. Caballero🇪🇸 · T. W. Donnelly🇺🇸
It is well known that coincidence quasielastic $(e, e^{'} N)$ reactions are not appropriate to analyze effects linked to parity violation due the presence of the fifth electromagnetic (EM) response $R^{T L^{'}}$ . Nevertheless, in this work we develop a fully relativistic approach to be applied to parity-violating (PV) quasielastic $(e, e^{'} N)$ processes. This is of importance as a preliminary step in the subsequent study of inclusive quasielastic PV $(e, e^{'})$ reactions. Moreover, our present analysis allows us to disentangle effects associated with the off-shell character of nucleons in nuclei, gauge ambiguities and the role played by the lower components in the nucleon wave functions, i.e., dynamical relativistic effects. This study can help in getting clear information on PV effects. Particular attention is paid to the relativistic plane-wave impulse approximation where the explicit expressions for the PV single-nucleon responses are shown for the first time.
nucl-thPRC(2015)·1 citation
06
Scaling of nuclear modification factors for hadrons and light nuclei
C. S. Zhou🇨🇳 · Y. G. Ma🇨🇳 · S. Zhang🇨🇳
The number of constituent quarks (NCQ-) scaling of hadrons and the number of constituent nucleons (NCN-) scaling of light nuclei are proposed for nuclear modification factors ( $R_{c p}$ ) of hadrons and light nuclei, respectively, according to the experimental investigations in relativistic heavy-ion collisions. Based on coalescence mechanism the scalings are performed for pions and protons in quark level, and light nuclei $d (d ˉ)$ and $^{3}$ He for nucleonic level, respectively, formed in Au + Au and Pb + Pb collisions and nice scaling behaviour emerges. NCQ or NCN scaling law of $R_{c p}$ can be respectively taken as a probe for quark or nucleon coalescence mechanism for the formation of hadron or light nuclei in relativistic heavy-ion collisions.
nucl-thnucl-exEPJA(2016)·8 citations
07
Nuclear Equation of State and Neutron Star Cooling
Yeunhwan Lim🇺🇸 · Chang Ho Hyun🇰🇷 · Chang-Hwan Lee🇰🇷
We investigate the cooling of neutron stars with relativistic and non-relativistic models of dense nuclear matter. We focus on the effects of uncertainties originated from the nuclear models, the composition of elements in the envelope region, and the formation of superfluidity in the core and the crust of neutron stars. Discovery of $2 M_{⊙}$ neutron stars PSR J1614-2230 and PSR J0343+0432 has triggered the revival of stiff nuclear equation of state at high densities. In the mean time, observation of a neutron star in Cassiopeia A for more than 10 years has provided us with very accurate data for the thermal evolution of neutron stars. Both mass and temperature of neutron stars depend critically on the equation of state of nuclear matter, so we first search for nuclear models that satisfy the constraints from mass and temperature simultaneously within a reasonable range. With selected models, we explore the effects of element composition in the evenlope region, and the existence of superfluidity in the core and the crust of neutron stars. Due to uncertainty in the composition of particles in the envelope region we obtain a range of cooling curves that can cover substantial region of observation data.
nucl-thastro-ph.HEIJMPE(2017)·36 citations
08
Nuclear Matter Incompressibility Effect on the Cross Section of Fusion Reactions with a weakly bound projectile
S. A. Seyyedi · H. Golnarkar
Fusion reactions with a weakly bound projectile are studied using the double-folding model along with a repulsive interaction modifying term. Using this modified potential, including nuclear matter incompressibility effects, the fusion reaction cross sections and suppression parameters are calculated for 9Be +209Bi,208Pb,29Si and 27Al reactions. The results show that applying these effects at energies near the Coulomb barrier improves the agreement between the calculated and experimental cross sections, and modifies the mean values of the suppression parameter.
nucl-thCPC(2015)·4 citations
09
A study of vorticity formation in high energy nuclear collisions
F. Becattini🇮🇹 · G. Inghirami🇩🇪 · V. Rolando🇮🇹 · A. Beraudo🇮🇹 · L. Del Zanna🇮🇹 · A. De Pace🇮🇹 · M. Nardi🇮🇹 · G. Pagliara🇮🇹 · V. Chandra🇮🇳
We present a quantitative study of vorticity formation in peripheral ultrarelativistic heavy ion collisions at sqrt(s)NN = 200 GeV by using the ECHO-QGP numerical code, implementing relativistic dissipative hydrodynamics in the causal Israel-Stewart framework in 3+1 dimensions with an initial Bjorken flow profile. We consider and discuss different definitions of vorticity which are relevant in relativistic hydrodynamics. After demonstrating the excellent capabilities of our code, which proves to be able to reproduce Gubser flow up to 8 fm/c, we show that, with the initial conditions needed to reproduce the measured directed flow in peripheral collisions corresponding to an average impact parameter b=11.6 fm and with the Bjorken flow profile for a viscous Quark Gluon Plasma with \eta/s=0.1 fixed, a vorticity of the order of some 10^{-2} c/fm can develop at freezeout. The ensuing polarization of Lambda baryons does not exceed 1.4% at midrapidity. We show that the amount of developed directed flow is sensitive to both the initial angular momentum of the plasma and its viscosity.
nucl-thhep-phEPJC(2015)·253 citations

Affiliations

first authorsco-authorsvia INSPIRE