Nuclear Theory·nucl-th

Wednesday·July 24, 2019

12 papers—8 primary·4 cross-listed

01
[Submitted on 22 Jul 2019]
Heavy quark dynamics in a hot magnetized QCD medium
Manu Kurian🇮🇳 · Santosh K. Das🇮🇳 · Vinod Chandra🇮🇳
The heavy quark drag and momentum diffusion have been investigated in a hot magnetized quark-gluon plasma, along the directions parallel and perpendicular to the magnetic field. The analysis is done within the framework of Fokker-Planck dynamics by considering the heavy quark scattering with thermal quarks and gluons at the leading order in the coupling constant. An extended quasiparticle model is adopted to encode the thermal QCD medium interactions in the presence of a magnetic field. Further, the higher Landau level effects on the temperature behaviour of the parallel and perpendicular components of the drag force and diffusion coefficients have studied. It has been observed that both the equation of state and the magnetic field play key roles in the temperature dependence of the heavy quark dynamics.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.09556 [pdf]
PRD(2019)·43 citations
02
[Submitted on 23 Jul 2019]
Selection of projectiles for producing trans-uranium nuclei in transfer reactions within an improved dinuclear system model
Long Zhu
The multinucleon transfer process is one promising approach for producing neutron-rich heavy nuclei. The favorable projectile-target combinations play a key role in experiments. As one important approach to investigate the multinucleon transfer process, one new version of the dinuclear system (DNS) model is developed. The improved version of the DNS model is shown in detail. Based on deformation degree of freedom in the improved DNS model, one way of calculating excitation energies of primary fragments is proposed. And the remarkable improvements for describing experimental data of producing trans-uranium nuclei is noticed. To produce trans-uranium nuclei, the collisions of 48Ca, 136Xe, and 238U projectiles with the 238U target are investigated within the improved DNS model. Based on the potential energy surface, the influence of projectiles on the probabilities of transferring neutrons and protons from the projectiles to the target are studied. One behavior is found that the transfer probabilities strongly depend on the projectiles in the neutron stripping process, while relatively weak projectile dependence is noticed in the proton transferring process. The 136Xe and 238U projectiles show great advantages of cross sections for producing neutron-rich trans-uranium nuclei, although the fission probabilities are large.
Comments:
11 figures, 9 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.09761 [pdf]
J.Phys.G(2020)·15 citations
03
[Submitted on 23 Jul 2019]
Non-adiabatic transitions and non-equilibrium statistics of deforming nuclei
Nishchal R. Dwivedi · Sudhir R. Jain
We establish a connection between macroscopic "heating or cooling" of a finite many-body quantum system and the non-adiabatic Landau-Zener-Stückelberg transitions between its quantum states. We have considered the well-known Nilsson model for describing the single-particle states of nuclei and subject the system to a random walk in the deformation space. This subsumes modelling of an evolving many-body system where the dynamics is chaotic. We discover a universality in the distribution of final "temperatures", beginning with a canonical equilibrium at some temperature $T$ . The quantum system is thrown out of equilibrium where free energy and work undergo fluctuations. These fluctuations are shown to respect Jarzynski inequality, and, the Bochkov-Kuzovlev equalities. We believe that this study will pave the way towards understanding non-equlibrium phenomena in other finite quantum systems like metallic clusters, quantum dots, and others.
Comments:
5 Figures, 2 Tables
Subjects:
Nuclear Theory (nucl-th); nlin.CD (nlin.CD); Nuclear Experiment (nucl-ex)
arXiv:
1907.09763 [pdf]
0 citations
04
[Submitted on 23 Jul 2019]
Trees and Islands -- Machine learning approach to nuclear physics
Nishchal R. Dwivedi
We implement machine learning algorithms to nuclear data. These algorithms are purely data driven and generate models that are capable to capture intricate trends. Gradient boosted trees algorithm is employed to generate a trained model from existing nuclear data, which is used for prediction for data of damping parameter, shell correction energies, quadrupole deformation, pairing gaps, level densities and giant dipole resonance for large number of nuclei. We, in particular, predict level density parameter for superheavy elements which is of great current interest. The predictions made by the machine learning algorithm is found to have standard deviation from 0.00035 to 0.73.
Comments:
8 Figures, 2 Tables
Subjects:
Nuclear Theory (nucl-th); Machine Learning (cs.LG); Nuclear Experiment (nucl-ex); Machine Learning (stat.ML)
arXiv:
1907.09764 [pdf]
1 citation
05
[Submitted on 23 Jul 2019]
Ignatyuk damping factor: A semiclassical formula
Nishchal R. Dwivedi · Saniya Monga · Harjeet Kaur · Sudhir R. Jain
Data on nuclear level densities extracted from transmission data or gamma energy spectrum store the basic statistical information about nuclei at various temperatures. Generally this extracted data goes through model fitting using computer codes like CASCADE. However, recently established semiclassical methods involving no adjustable parameters to determine the level density parameter for magic and semi-magic nuclei give a good agreement with the experimental values. One of the popular ways to paramaterize the level density parameter which includes the shell effects and its damping was given by Ignatyuk. This damping factor is usually fitted from the experimental data on nuclear level density and it comes around 0.05 $M e V^{- 1}$ . In this work we calculate the Ignatyuk damping factor for various nuclei using semiclassical methods.
Comments:
9 Figures, 1 Table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1907.09770 [pdf]
IJMPE(2019)·10 citations
06
[Submitted on 23 Jul 2019]
Novel chiral Hamiltonian and observables in light and medium-mass nuclei
V. Somà🇫🇷 · P. Navrátil🇨🇦 · F. Raimondi🇫🇷 · C. Barbieri🇬🇧 · T. Duguet🇫🇷
A novel parameterisation of a Hamiltonian based on chiral effective field theory is introduced. Specifically, three-nucleon operators at next-to-next-to-leading order are combined with an existing (and successful) two-body interaction containing terms up to next-to-next-to-next-to-leading order. The resulting potential is labelled $N N$ + $3 N (lnl)$ . The objective of the present work is to investigate the performance of this new Hamiltonian across light and medium-mass nuclei. Binding energies, nuclear radii and excitation spectra are computed using no-core shell model and self-consistent Green's function approaches. Calculations with $N N$ + $3 N (lnl)$ are compared to two other representative Hamiltonians currently in use, namely NNLO $_{sat}$ and the older $N N$ + $3 N (400)$ . Overall, the performance of the novel interaction is very encouraging. In light nuclei, total energies are generally in good agreement with experimental data. Known spectra are also well reproduced with a few notable exceptions. The good description of ground-state energies carries on to heavier nuclei, all the way from oxygen to nickel isotopes. Except for those involving excitation processes across the $N = 20$ gap, which is overestimated by the new interaction, spectra are of very good quality, in general superior to those obtained with NNLO $_{sat}$ . Although largely improving on $N N$ + $3 N (400)$ results, charge radii calculated with $N N$ + $3 N (lnl)$ still underestimate experimental values, as opposed to the ones computed with NNLO $_{sat}$ that successfully reproduce available data on nickel. On the whole, the new two- plus three-nucleon Hamiltonian introduced in the present work represents a promising alternative to existing nuclear interactions.
Comments:
21 pages, 22 figures, matches published version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1907.09790 [pdf]
PRC(2020)·201 citations
07
[Submitted on 23 Jul 2019]
Spin chemical potential for relativistic particles with spin 1/2
Wojciech Florkowski · Avdhesh Kumar · Radoslaw Ryblewski
We analyze algebraic structure of a relativistic semi-classical Wigner function of particles with spin 1/2 and show that it consistently includes information about the spin density matrix both in two-dimensional spin and four-dimensional spinor spaces. This result is subsequently used to explore various forms of equilibrium functions that differ by specific incorporation of spin chemical potential. We argue that a scalar spin chemical potential should be momentum dependent, while its tensor form may be a function of space-time coordinates only. This allows for the use of the tensor form in local thermodynamic relations. We furthermore show how scalar and tensor forms can be linked to each other.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.09835 [pdf]
Acta Phys.Polon.B(2020)·22 citations
08
[Submitted on 23 Jul 2019]
Asymmetry for tensor $t_{2 j}$ and vector $t_{1 i}$ polarizations with taking into account the deuteron wave function in coordinate space
V.I. Zhaba
The analytic forms of deuteron wave function in coordinate space were applied for theoretical calculations of full set asymmetries of tensor $t_{2 j}$ and vector $t_{1 i}$ polarizations. Nucleon-nucleon realistic phenomenological potentials of Nijmegen group (Nijm1, Nijm2, Nijm93, Reid93) and Argonne group (Argonne v18) as well as other widely used and popular potentials (OBEPC, MT, Paris) are used for numerical calculations. The angular asymmetry is calculated in the range of momentums 0-7 fm $^{- 1}$ . The values of the asymmetry $t_{ij,}$ by polarization type and with each other, are analysed. This is the angular-momentum dependence of values vector $t_{1 i} (p, θ_{e})$ and tensor $t_{2 i} (p, θ_{e})$ polarizations in 3D format at momentums 0-7 fm $^{- 1}$ and scattering angles 1-180 degrees were calculated and compared for Reid93 potential. The perspectives of further application of the obtained results for calculating the values of the cross-sections, asymmetries and other characteristics of processes with the participation of a deuteron are discussed.
Comments:
10 pages, 10 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.09853 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE