Nuclear Theory·nucl-th

Thursday·November 8, 2018

12 papers—7 primary·5 cross-listed

01
Matrix Model of Strength Distribution: Extension and Phase Transition
Arun Kingan · Larry Zamick
In this work we extend a previous study of matrix models of strength distributions. We still retain the nearest neighbor coupling mode but we extend the values the coupling parameter v. We consider extremes, from very smal v to very large v. We first use the same transiiton operator as before \textless{}n T(n+1)\textgreater{} =constat(=1). For this case we get an exponential decreasefor small v but we get a phase transition beyond v=10. In that case we get an even-odd effect-separate exponentials for even n and for odd n. We now also consider also the dipole choice--where \textless{}nT(n+1)\textgreater{} = $(n + 1)$ .
nucl-thnucl-exquant-phIJMPE(2018)·6 citations
02
Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes
N. N. Arsenyev🇷🇺 · A. P. Severyukhin🇷🇺 · V. V. Voronov🇷🇺 · Nguyen Van Giai🇫🇷
We study the effects of the phonon-phonon coupling on the low-energy electric dipole response within a microscopic model based on an effective Skyrme interaction. The finite rank separable approach for the quasiparticle random phase approximation is used. Choosing as an example the isotopic chain of Calcium, we show the ability of the method to describe the low-energy $E 1$ strength distribution. With one and the same set of parameters we describe available experimental data for $^{48}$ Ca and predict the electric dipole strength function for $^{50}$ Ca.
nucl-thEPJ Web Conf.(2018)·2 citations
03
Linear response theory for Gogny interaction
D. Davesne🇫🇷 · J. Navarro🇪🇸 · A. Pastore🇬🇧
We present the formalism of the linear response theory in symmetric nuclear matter for a finite-range central interaction interaction including zero-range spin-orbit and tensor components.
nucl-thActa Phys.Polon.Supp.(2019)·1 citation
04
Two-nucleon emitters within a pseudostate approach
J. Casal · J. Gómez-Camacho
A method to identify and characterize three-body resonances in a discrete basis is discussed in the context of two-nucleon emitters. For this purpose, a resonance operator is introduced and diagonalized in a basis of energy pseudostates within the hyperspherical formalism. Then, the energy and width of the resonance are obtained from its time dependence. The approach is illustrated for $^{16}$ Be ( $^{14} Be + n + n$ ).
nucl-thSpringer Proc.Phys.(2020)·0 citations
05
Temperature dependence of the volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model
A.N. Antonov · D.N. Kadrev · M.K. Gaidarov · P. Sarriguren · E. Moya de Guerra
The temperature dependence of the volume and surface components of the nuclear symmetry energy (NSE) and their ratio is investigated in the framework of the local density approximation (LDA). The results of these quantities for finite nuclei are obtained within the coherent density fluctuation model (CDFM). The CDFM weight function is obtained using the temperature-dependent proton and neutron densities calculated through the HFBTHO code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. We present and discuss the values of the volume and surface contributions to the NSE and their ratio obtained for the Ni, Sn, and Pb isotopic chains around double-magic $^{78}$ Ni, $^{132}$ Sn, and $^{208}$ Pb nuclei. The results for the $T$ -dependence of the considered quantities are compared with estimations made previously for zero temperature showing the behavior of the NSE components and their ratio, as well as with the available experimental data. The sensitivity of the results on various forms of the density dependence of the symmetry energy is studied. We confirm the existence of `kinks' of these quantities as functions of the mass number at $T = 0$ MeV for the double closed-shell nuclei $^{78}$ Ni and $^{132}$ Sn and the lack of `kinks' for the Pb isotopes, as well as the disappearance of these kinks as the temperature increases.
nucl-thPRC(2018)·19 citations
06
Phase transitions and Bose-Einstein condensation in alpha-nucleon matter
L. M. Satarov · I. N. Mishustin · A. Motornenko · V. Vovchenko · M. I. Gorenstein · H. Stoecker
The equation of state and phase diagram of isospin-symmetric chemically equilibrated mixture of alpha particles and nucleons are studied in the mean-field approximation. The model takes into account the effects of Fermi and Bose statistics for nucleons and alphas, respectively. We use Skyrme-like parametrization of the mean-field potentials as functions of partial densities, which contain both attractive and repulsive terms. Parameters of these potentials are chosen by fitting known properties of pure nucleon- and pure alpha matter at zero temperature. The sensitivity of results to the choice of the alpha-nucleon attraction strength is investigated. The phase diagram of the alpha-nucleon mixture is studied with a special attention paid to the liquid-gas phase transitions and the Bose-Einstein condensation of alpha particles. We have found two first-order phase transitions, stable and metastable, which differ significantly by the fractions of alpha particles. It is shown that states with alpha condensate are metastable.
nucl-thPRC(2019)·19 citations
07
Towards a novel energy density functional for beyond-mean-field calculations with pairing and deformation
T. Haverinen🇫🇮 · M. Kortelainen🇫🇮 · J. Dobaczewski🇫🇮 · K. Bennaceur🇫🇷
We take an additional step towards the optimization of the novel finite-range pseudopotential at constrained Hartree-Fock-Bogolyubov level and implement an optimization procedure within an axial code using harmonic oscillator basis. We perform the optimization using three different numbers of the harmonic oscillator shells. We apply the new parameterizations in the O-Kr part of the nuclear chart and isotopic chain of Sn, and we compare the results with experimental values and those given by a parameterization obtained using a spherical code.
nucl-thActa Phys.Polon.B(2019)·1 citation
08
Skyrmions and clustering in light nuclei
Carlos Naya🇬🇧 · Paul Sutcliffe🇬🇧
One of the outstanding problems in modern nuclear physics is to determine the properties of nuclei from the fundamental theory of the strong force, quantum chromodynamics (QCD). Skyrmions offer a novel approach to this problem by considering nuclei as solitons of a low energy effective field theory obtained from QCD. Unfortunately, the standard theory of Skyrmions has been plagued by two significant problems, in that it yields nuclear binding energies that are an order of magnitude larger than experimental nuclear data, and it predicts intrinsic shapes for nuclei that fail to match the clustering structure of light nuclei. Here we show that extending the standard theory of Skyrmions, by including the next lightest subatomic meson particles traditionally neglected, dramatically improves both these aspects. We find Skyrmion clustering that now agrees with the expected structure of light nuclei, with binding energies that are much closer to nuclear data.
↳ hep-thnucl-thPRL(2018)·68 citations
09
The origin of the nucleon mass
Cédric Lorcé (Ecole polytechnique, CPHT)🇫🇷
It is often claimed that 98% of the nucleon mass is generated by quantum chromodynamics. The decomposition of the nucleon mass based on the trace of the energy-momentum tensor suggests that gluons play by far a dominant role. About 25 years ago, Ji proposed another decomposition based on the energy component of the energy-momentum tensor, leading to a quite different picture. Recently, we critically revisited these decompositions and argued that both overlooked pressure effects. In particular we showed that Ji's decomposition, although mathematically correct, makes little sense from a physical point of view. We identify the proper mass decomposition along with a balance equation for the pressure forces.
↳ hep-phnucl-thSpringer Proc.Phys.(2020)·7 citations
10
Doubly-heavy baryons, tetraquarks, and related topics
Jean-Marc Richard🇫🇷 · Alfredo Valcarce🇪🇸 · Javier Vijande🇪🇸
We review the physics of doubly-heavy baryons $QQq$ and tetraquarks $QQ q ˉ q ˉ$ . For the latter, the stability is reached for large enough mass ratio $M / m$ , even when spin forces and color mixing are neglected. It is thus customarily claimed that $bb q ˉ q ˉ$ in its ground state cannot decay into $b q ˉ + b q ˉ$ . In some model, $cc u ˉ d ˉ$ is shown to be stable if color mixing and spin effects are properly taken into account. It is conjectured that some $b c q ˉ q ˉ^{'}$ benefits from favorable adjustments of the gluon tubes in the confinement regime. Some recent studies of pentaquarks and hexaquarks are also summarized.
↳ hep-phnucl-thBled Workshops Phys.(2018)·5 citations
11
Chemical Equilibration in Hadronic Collisions
Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪
We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma using the first principles method of QCD effective kinetic theory, accurate at weak coupling. In longitudinally expanding systems--relevant for relativistic nuclear collisions--we find that for realistic couplings chemical equilibration takes place after hydrodynamization, but well before local thermalization. We estimate that hadronic collisions with final state multiplicities $d N_{ch} / d η ≳ 1 0^{2}$ live long enough to reach approximate chemical equilibrium, which is consistent with the saturation of strangeness enhancement observed in proton-proton, proton-nucleus and nucleus-nucleus collisions.
↳ hep-phnucl-thPRL(2019)·103 citations
12
Chemical Equilibration in Weakly Coupled QCD
Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪
We study thermalization, hydrodynamization, and chemical equilibration in out-of-equilibrium Quark-Gluon Plasma starting from various initial conditions using QCD effective kinetic theory, valid at weak coupling. In non-expanding systems gauge bosons rapidly lose information of the initial state and achieve kinetic equilibrium among themselves, while fermions approach the equilibrium distribution only at later time. In systems undergoing rapid longitudinal expansion, both gluons and quarks are kept away from equilibrium by the expansion, but the evolution is well described by fluid dynamics even before local thermal equilibrium is reached. For realistic couplings we determine the ordering between the separate hydrodynamization, chemical equilibration and thermalization time scales to be $τ_{hydro} < τ_{chem} < τ_{therm}$ .
↳ hep-phnucl-thPRD(2019)·104 citations

Affiliations

first authorsco-authorsvia INSPIRE