Nuclear Theory·nucl-th

Friday·January 1, 2021

16 papers—8 primary·8 cross-listed

01
Jets as a probe of the quark-gluon plasma
Jasmine Brewer🇺🇸
The suppression and modification of high-energy objects, like jets, in heavy-ion collisions provide an important window to access the degrees of freedom of the quark-gluon plasma on different length scales. Despite increasingly precise and differential measurements of the properties of jets in heavy-ion collisions, however, it has remained challenging to use jets to make unambiguous and model-independent statements about the quark-gluon plasma. Here I will give a personal take on some origins of these challenges, including the difficulty of modelling and biases from jet selection that obfuscate the direct interpretation of jet modification measurements. I will discuss a few model studies that have helped to disentangle the source of non-intuitive effects in measurements, and finally highlight data-driven approaches as an interesting opportunity toward studying the quark-gluon plasma in a model-independent way using jets.
nucl-thPoS(2021)·3 citations
02
A Nonequilibrium Information Entropy Approach to Ternary Fission of Actinides
G. Röpke · J. B. Natowitz · H. Pais
Ternary fission of actinides probes the state of the nucleus at scission. Light clusters are produced in space and time very close to the scission point. Within the nonequilibrium statistical operator method, a generalized Gibbs distribution is constructed from the information given by the observed yields of isotopes. Using this relevant statistical operator, yields are calculated taking excited states and continuum correlations into account, in accordance with the virial expansion of the equation of state. Clusters with mass number $A \leq 10$ are well described using the nonequilibrium generalizations of temperature and chemical potentials. Improving the virial expansion, in-medium effects may become of importance in determining the contribution of weakly bound states and continuum correlations to the intrinsic partition function. Yields of larger clusters, which fail to reach this quasi-equilibrium form of the relevant distribution, are described by nucleation kinetics, and a saddle-to-scission relaxation time of about 7000 fm/c is inferred. Light charged particle emission, described by reaction kinetics and virial expansions, may therefore be regarded as a very important tool to probe the nonequilibrium time evolution of actinide nuclei during fission.
nucl-thPRC(2021)·12 citations
03
Skyrme-Hartree-Fock calculations of nuclear properties in the drip-point region of neutron star crust
Uwe Heinzmann · Igor Mishustin · Stefan Schramm
In the present paper we explore the neutron-drip region of cold non-rotating isolated neutron stars. We have performed extended nuclear-structure calculations for nuclei embedded in the electron gas. For modeling the outer crust we use a set of Wigner-Seitz cells, where every cell contains one nucleus surrounded by a cloud of relativistic electrons. Above the drip point a non-relativistic neutron gas occurs in the cell. These calculations are carried out within the Hartree-Fock approach in combination with Skyrme effective interactions. For every baryon density we have determined the configuration with a minimal total energy. The drip elements and corresponding drip densities have been determined for about 240 different parametrizations of Skyrme forces used in the literature. We demonstrate that the calculated drip-point densities depend essentially on the Skyrme parametrization used. Even the drip elements and the occupied shells in the drip region differ for different parametrizations. We have found that the number of neutrons building the neutron gas at the drip point also depends essentially on the Skyrme force chosen. Nevertheless, the number density of the neutron gas in the drip-region is more or less the same ( $\sim 1 0^{- 5} \frac{n e u t r o n s}{f m ^{3}}$ ). The drip densities obtained within our approach are generally lower than predicted earlier.
nucl-th0 citations
04
Inclusive Breakup Cross Sections in Reactions Induced by the Nuclides $^{6}$ He and $^{6, 7}$ Li in the Two-Body Cluster Model
L. A. Souza · E. V. Chimanski · B. V. Carlson
Calculations of inclusive $α$ particle production are performed to interpret reaction experimental data induced by the two-neutron halo $^{6}$ He and the isotopes $^{6, 7}$ Li on different target nuclei. We have implemented the zero-range post-form DWBA to compute the elastic and nonelastic breakup cross sections. Integrated cross sections, angular distributions and spectra are presented. Projectiles are approximated as two-body clusters, namely $^{6}$ He as $α$ +dineutron and $^{6}$ Li ( $^{7}$ Li) interpreted as $α$ +deuteron(triton). The São Paulo optical potential is employed in the calculation of the distorted wave functions for the incident channels, while standard phenomenological interactions are used for the fragment-target interactions. Calculations for $^{6}$ Li and $^{7}$ Li furnish a good description of the data, while the reaction involving $^{6}$ He is found to be a complicated case, where data interpretation is still considered a major obstacle. The present analysis identifies an overall large contribution from inclusive breakup emissions for all the cases studied.
nucl-thPRC(2021)·6 citations
05
Woods-Saxon-type of mean-field potentials with effective mass derived from the D1S Gogny force
A. Bhagwat🇮🇳 · M. Centelles🇪🇸 · X. Viñas🇪🇸 · P. Schuck🇫🇷
Analytic average mean-field potentials of the Fermi-function (Woods-Saxon) type for the whole nuclear chart with space-dependent effective mass are deduced from the D1S Gogny force. Those ready-for-use potentials are advertised as an alternative to other existing phenomenological mean-field potentials.
nucl-thPRC(2021)·7 citations
06
Fermions with long and finite range interactions on a quantum ring
A. W. Bray🇦🇺 · C. Simenel🇦🇺
Background: Idealised systems are commonly used in nuclear physics and condensed matter. For instance, the construction of nuclear energy density functionals involves properties of infinite matter, while neutron drops are used to test nuclear interactions and approximations to the nuclear many-body problem. In condensed matter, quantum rings are also used to study properties of electron systems. Purpose: To investigate the possibility to use quantum rings with systems of nucleons including many-body correlations. Methods: A quantum ring model of a finite number of same spin fermions is developed. Several attractive and repulsive interactions with finite and infinite ranges are considered. Quantum Monte Carlo calculations are used to provide exact ground-state energies. Comparisons with analytical Hartree-Fock solutions are used to get an insight into the role of correlations. Results: Hartree-Fock results with no breaking of space translational symmetry are able to describe many systems. However, additional spatial correlations are required in the case of dense systems with a strong short-range repulsion, or with attractive interactions in large rings. Conclusions: Self-bound systems of fermions with spatial correlations produced by basic features of the nuclear interactions can be described on a quantum ring, encouraging applications with realistic interactions, as well as investigations with higher dimensional geometries such as spherium.
nucl-thPRC(2021)·1 citation
07
Microscopic-Macroscopic Approach for Ground-State Energies Based on the Gogny Force with the Wigner-Kirkwood Averaging Scheme
A. Bhagwat🇮🇳 · M. Centelles🇪🇸 · X. Viñas🇪🇸 · P. Schuck🇫🇷
In the previous paper I \cite{bhagwat20} we have shown that self-consistent Extended Thomas-Fermi (ETF) potentials and densities associated with a given finite-range interaction can be parametrized by generalized Fermi distributions. As a next step, a comprehensive calculation of ground-state properties of a large number of spherical and deformed even-even nuclei is carried out in the present work using the Gogny D1S force within the ETF scheme. The parametrized ETF potentials and densities of paper I are used to calculate the smooth part of the energy and the shell corrections within the Wigner-Kirkwood semiclassical averaging scheme. It is shown that the shell corrections thus obtained, along with a simple liquid drop prescription, yield a good description of ground-state masses and potential energy surfaces for nuclei spanning the entire periodic table.
nucl-thPRC(2021)·6 citations
08
Self-consistent conversion of a one-component bulk viscous fluid to particles
Denes Molnar ((1) Purdue University, (2) Wigner Research Center for Physics, Budapest)
Comparison of heavy-ion experiments to fluid dynamics simulations requires the conversion of the fluid to particles. Extending the approach in Molnar & Wolff, PRC 95, 024903 (2017), this work presents self-consistent bulk viscous corrections from kinetic theory for a one-component system with isotropic $2 \to 2$ interactions. The phase space corrections are contrasted to the Grad ansatz and also to corrections obtained from the relaxation time approximation. In addition, the bulk viscosity of the system is calculated and compared with the Grad result, as well as the $ζ \propto (1 - 3 c_{s}^{2})^{2} η$ relation between shear and bulk viscosity near the conformal limit. The possible influence of various bulk correction choices on differential elliptic flow $v_{2} (p_{T})$ in heavy-ion collisions is also estimated.
nucl-thhep-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE