Nuclear Theory·nucl-th

Tuesday·May 12, 2020

25 papers—12 primary·13 cross-listed

01
Thermal transport in a weakly magnetized hot QCD medium
Manu Kurian🇮🇳
The thermal transport coefficients in a weakly magnetized quark-gluon plasma have been investigated within the ambit of a quasiparticle model to encode the effects of the realistic equation of state. The presence of a weak magnetic field leads to the Hall-type conductivity associated with thermal transport in the medium. An effective covariant kinetic theory has been employed to quantify the thermal dissipation while incorporating the mean field contributions in the medium. The interplay of thermal transport and electric charge transport in the weakly magnetized medium has been explored in terms of the Wiedemann-Franz law. Strong violation of the Wiedemann-Franz law has been observed in temperature regimes near to the transition temperature. The behaviour of thermal conductivity in the strong magnetic field limit has also been studied. It is observed that both the magnetic field and equation of state have a significant impact on the thermal dissipation in the medium.
nucl-thPRD(2020)·19 citations
02
Giant dipole resonance and shape evolution in Nd isotopes within TDHF method
A. Ait Ben Mennana · Y. EL Bassem · M. Oulne
The isovector giant dipole resonance (IVGDR) in even-even Nd isotopes from A=124 to A=160 is studied in the framework of time-dependent Hartree-Fock (TDHF) with Skyrme forces SkI3, SVbas, SLy5 and SLy6. The dipole strength is calculated and compared with the experimental data on photon absorption cross section $σ_{γ}$ . An overall agreement between them is obtained. The dipole strengths in $^{124 - 140} Nd$ and $^{152 - 160} Nd$ are predicted. In addition, the correlation between the quadrupole deformation parameter $β_{2}$ and the splitting $Δ E / E ˉ_{m}$ of the giant dipole resonance (GDR) spectra is studied. The results confirm that $Δ E / E ˉ_{m}$ is proportional to $β_{2}$ . Shape phase transition in Nd isotopes is also investigated in the light of IVGDR.
nucl-thPhys.Scripta(2020)·9 citations
03
Timescales of quantum equilibration, dissipation and fluctuation in nuclear collisions
C. Simenel · K. Godbey · A.S. Umar
Understanding the dynamics of equilibration processes in quantum systems as well as their interplay with dissipation and fluctuation is a major challenge in quantum many-body theory. The timescales of such processes are investigated in collisions of atomic nuclei using fully microscopic approaches. Results from time-dependent Hartree-Fock (TDHF) and time-dependent random-phase approximation (TDRPA) calculations are compared for 13 systems over a broad range of energies. The timescale for full mass equilibration ( $\sim 2 \times 1 0^{- 20}$ s) is found to be much larger than timescales for neutron-to-proton equilibration, kinetic energy and angular momentum dissipations which are on the order of $1 0^{- 21}$ s. Fluctuations of mass numbers in the fragments and correlations between their neutron and proton numbers build up within only a few $1 0^{- 21}$ s. This indicates that dissipation is basically not impacted by mass equilibration, but is mostly driven by the exchange of nucleons between the fragments.
nucl-thnucl-exquant-phPRL(2020)·66 citations
04
Evolution of clustering structure through the momentum distributions in $^{8 - 10}$ Be isotopes
Songjie Li · Takayuki Myo · Qing Zhao · Hiroshi Toki · Hisashi Horiuchi · Chang Xu · Jian Liu · Mengjiao Lyu · Zhongzhou Ren
We investigate the evolution of clustering structure through the momentum distributions in the $^{8 - 10}$ Be isotopes. The nucleon dynamics within the inter-cluster antisymmetrization are discussed via the momentum distribution of a Brink type $α$ - $α$ wave function. For the state with a small $α$ - $α$ distance, we observe a significant depression with a dip structure at zero-momentum and an enhanced tail at relatively higher momentum region. In addition, we find the "cluster structure" in the intrinsic frame of momentum space, which is complementary to its significant $α$ -cluster dissolution in the coordinate space because of the strong antisymmetrization. For the physical $^{8 - 10}$ Be isotopes, the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave functions are adopted. The evolution from the dilute clustering state to the compact one is demonstrated by a successive depression at the zero-momentum of nucleon distribution for the two $α$ -clusters within $^{8 - 10}$ Be isotopes. For the compact $^{10}$ Be nucleus, the momentum distribution of all nucleons shows significant depression at zero-momentum with a dip structure, which is found to be contributed by both the inter-cluster antisymmetrization and the $p$ -orbit occupation of the valence neutrons. This study proposes a new window for the investigations of the $α$ -clustering effects via the low-momentum components of nuclei, which is expected to be extended to the heavier nuclear clustering states.
nucl-thPRC(2020)·6 citations
05
Manifestation of the divergence between antisymmetrized-molecular-dynamics and container pictures of $^{9}$ Be via $^{9}$ Be( $p, p n$ ) $^{8}$ Be knockout reaction
Nguyen Tri Toan Phuc · Mengjiao Lyu · Yohei Chiba · Kazuyuki Ogata
We propose a new approach to probe the spatial extension of the valence neutron orbital in the $^{9}$ Be nucleus via the $^{9}$ Be( $p, p n$ ) $^{8}$ Be knockout reaction. This property of the nuclear molecular orbital has not been established in previous experimental studies and divergence exists between the theoretical descriptions of $^{9}$ Be from different perspectives, \textit{i.e.}, the antisymmetrized molecular dynamics and the container pictures of cluster dynamics. These pictures are represented by two different well-proven microscopic models, the antisymmetrized molecular dynamics (AMD) and Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave functions. The corresponding reduced width amplitudes (RWAs) in the $^{8}$ Be $+ n$ channel are extracted from both the AMD and THSR wave functions, and they are found to describe drastically different valence-nucleon motion, which shows the theoretical ambiguity in describing the $π$ -orbitals in $^{9}$ Be. Using the RWAs as input, the physical observables of the $^{9}$ Be( $p, p n$ ) $^{8}$ Be knockout reaction are predicted by the distorted-wave impulse approximation (DWIA) framework. The magnitudes of the triple-differential cross sections (TDX) are found to be highly sensitive to the RWA input. It is concluded that the $^{9}$ Be( $p, p n$ ) $^{8}$ Be knockout reaction could provide a feasible probing for the subtle differences between several structure models manifesting through the spatial extension of the $π$ -orbital in the $^{9}$ Be nucleus.
nucl-thPLB(2021)·2 citations
06
Productions of high energy neutrons by interactions between deuteron beam and thick target
Wu Sun · Weiwei Qiu · Jun Su
The cross sections of high energy neutron-induced spallation is useful for studying the transmutation of long-life fission products. However, due to the difficulty of obtaining high-energy neutrons, the experimental data are still scarce. The present work studies the possibility to produce high energy neutrons by interactions between deuteron beam and thick target. The Geant4 toolkit is applied to simulate the interaction between the deuteron beam and thick target. An analytical method is also developed to calculate the neutron yields emitted in the interaction between the deuteron beam and thick target. The input cross section data is not only taken from the TEDNL-2017 library but also calculated by the isospin-dependent quantum molecular dynamics model. It is indicated that it is possible to produce high energy neutron by deuteron beam interaction with matter. If one wants to get high energy neutrons, low-Z matter, thin target, and small emission angle may be considered.
nucl-th0 citations
07
The study of Nuclear binding energy for $A \geq 100$ based on Odd-Even staggering of nuclear masses
B. B. Jiao
The existing nuclear masses formula and nuclear masses model has undoubtedly achieved very good results, but it is still not satisfactory for some nuclear masses. Although there are many studies in Odd-Even staggering (OES) of nuclear masses, but the research on nuclear masses by using the systematicness of OES is indeed very few. Our purpose in this paper is to describe an empirical formula for Odd-Even staggering of nuclear masses that can be useful in describing and predicting nuclear masses. We empirically obtained the formula of odd-Z (odd-N) nuclei and even-Z (even-N) nuclei based on studying the OES of nuclear masses (AME2012). With the proton (neutron) empirical pairing gap from the OES of the binding energies and AME2012 database, the root-mean-square deviation of even-Z nuclei and odd-Z nuclei that we have successfully obtained 208 keV and 238 keV, respectively. The RMSD of even-N nuclei and odd-N nuclei is 222 keV and 240 keV. The result shows that our predicted values are compared well with values in AME2016, and some predicted values agree better with the experimental values. These results demonstrate that our empirical formulas have good accuracy and reliability. Another advantage of these formulas is that they use less known nuclear masses to predict unknown nuclear masses. In addition, this paper also uses BP neural network to study proton Odd-Even staggering of nuclear masses (even-Z and odd-Z nuclei) and neutron Odd-Even staggering of nuclear masses (even-N and odd-N nuclei). The RMSD of even-Z and odd-Z nuclei is 141 keV and 159 keV; the RMSD of even-N and odd-N nuclei is 150 keV and 160 keV. The results show that the RMSD of nuclear masses based on neural network 60-80 keV decrease than that based on empirical formula (the accuracy is increased by about 32%). Accurate nuclear mass is helpful to the research of nuclear physics, nuclear technology and astrophysics.
nucl-th0 citations
08
Non-resonant Density of States Enhancement at Low Energies for Three or Four Neutrons
Michael D. Higgins · Chris H. Greene · Alejandro Kievsky · Michele Viviani
The low energy systems of three or four neutrons are treated within the adiabatic hyperspherical framework, yielding an understanding of the low energy quantum states in terms of an adiabatic potential energy curve. The dominant low energy potential curve for each system, computed here using widely accepted nucleon-nucleon interactions with and without the inclusion of a three-nucleon force, shows no sign of a low energy resonance. However, both systems exhibit a low energy enhancement of the density of states, or of the Wigner-Smith time-delay, which derives from long-range universal physics analogous to the Efimov effect. That enhancement could be relevant to understanding the low energy excess of correlated 4-neutron ejection events observed experimentally in a nuclear reaction by Kisamori et al.
nucl-thPRL(2020)·42 citations
09
A Fourier-Cumulant Analysis for Multiharmonic Flow Fluctuation
Seyed Farid Taghavi🇩🇪
The Fourier analysis of the final particle distribution followed by cumulant study of the Fourier coefficient event-by-event fluctuation is one of the main approaches for testing the collective evolution in the heavy-ion collision. Using a multidimensional generating function, we propose a method to extract any possible cumulant of multiharmonic flow fluctuations and classify them in terms of the order of cumulants and harmonics involved in them. In particular, we show that there are 33 distinct cumulants with orders $2, 3, 4, 5$ and harmonics $2, 3, 4, 5$ . We compute the normalized version of these cumulants from hydrodynamic simulation for Pb--Pb collisions based on {\tt T $_{R}$ ENTo}+{\tt VISH2+1}+{\tt UrQMD}. We compare the simulation with those normalized cumulants that the LHC has measured and predict the unmeasured ones. Comparing the initial and final state fluctuation normalized cumulants, we compute the linear and nonlinear hydrodynamic response couplings. We finally introduce the genuine three-particle correlation function containing information of all third-order cumulants.
nucl-thhep-phnucl-exEPJC(2021)·15 citations
10
Thermal Fluctuations in Nuclear Pasta
M. E. Caplan🇺🇸 · C. R. Forsman🇺🇸 · A. S. Schneider🇸🇪
Despite their astrophysical relevance, nuclear pasta phases are relatively unstudied at high temperatures. We present molecular dynamics simulations of symmetric nuclear matter with several topologies of `lasagna' at a range of temperatures to study the pasta-uniform transition. Using the Minkowski functionals we quantify trends in the occupied volume, surface area, mean breadth, and Euler characteristic. The amplitude of surface displacements of the pasta increase with temperature which produce short lived topological defects such as holes and filaments near melting, resulting in power laws for increasing surface curvature with temperature. We calculate the static structure factor and report the shear viscosity and thermal conductivity of pasta, finding that the shear viscosity is minimized at the melting temperature. These results may have implications for the thermoelastic properties of nuclear pasta and finite temperature corrections to the equation of state at pasta densities.
nucl-thastro-ph.HEcond-mat.softPRC(2021)·17 citations
11
Laser-nucleus interactions in the sudden regime
Sergei Kobzak · Hans A. Weidenmüller · Adriana Pálffy
The interaction between medium-weight nuclei and a strong zeptosecond laser pulse of MeV photons is investigated theoretically. Multiple absorption of photons competes with nuclear equilibration. We investigate the sudden regime. Here the rate of photon absorption is so strong that there is no time for the nucleus to fully equilibrate after each photon absorption process. We follow the temporal evolution of the system in terms of a set of rate equations. These account for dipole absorption and induced dipole emission, equilibration (modeled in terms of particle-hole states coupled by the residual nuclear interaction), and neutron decay (populating a chain of proton-rich nuclei). Our results are compared with earlier work addressing the adiabatic regime where equilibration is instantaneous. We predict the degree of excitation and the range of nuclei reached by neutron evaporation. These findings are relevant for planning future experiments.
nucl-thnucl-exPRC(2021)·3 citations
12
Exploring the $Λ$ -deuteron interaction via correlations in heavy-ion collisions
J. Haidenbauer🇩🇪
$Λ$ -deuteron two-particle momentum correlation functions, to be measured in high-energy heavy-ion collisions, are investigated. In particular, the question is addressed whether such correlations can serve as an additional and alternative source of information on the elementary $Λ N$ interaction. The study is performed within the Lednicky-Lyuboshits formalism, utilizing an effective range expansion for the two relevant $S$ -wave $Λ d$ amplitudes with parameters taken from the literature. It is found that in collisions characterized by a large emitting source the $Λ d$ correlation function is predominatly sensitive to the quartet state ( $^{4} S_{3/2}$ ). In contrast, for small source sizes the contribution from the doublet partial wave ( $^{2} S_{1/2}$ ) could be significant. Though the latter is constrained by the hypertriton binding energy, its present experimental uncertainty impedes an accurate determination of the doublet amplitude and, in turn, complicates conclusions on the quartet state.
nucl-thhep-phPRC(2020)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE