Nuclear Theory·nucl-th

Thursday·April 27, 2017

9 papers—6 primary·3 cross-listed

01
[Submitted on 25 Apr 2017]
Probing the spacetime evolution of heavy ion collisions with photons and dileptons
Jean-François Paquet🇺🇸
Photons and dileptons are emitted throughout the evolution of the deconfined nuclear medium produced in heavy ion collisions. As such they can provide valuable information about the different phases of the medium, and complement hadronic measurements and other observables. In this work, recent developments related to electromagnetic emissions at early time, in the cross-over region, and at late times are reviewed. The spacetime description of the nuclear medium from a hydrodynamic model of heavy ion collisions is used to provide context and guide the discussion.
Comments:
8 pages, 4 figures, contribution to Quark Matter 2017 proceedings
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.07842 [pdf]
NPA(2017)·23 citations
02
[Submitted on 25 Apr 2017]
Equation of state of a quark-meson mixture in the improved-PNJL model at finite chemical potential
Juan M. Torres-Rincon🇩🇪 · Joerg Aichelin🇫🇷
We study the equation of state of QCD using an improved version of the three-flavor Polyakov-Nambu-Jona-Lasinio model beyond the mean-field approximation. It incorporates the effects of unquenched quarks into the Polyakov-loop effective potential, as well as mesonic contributions to the grand-canonical potential. We study in full detail the calculation of the thermodynamical potential in this approach and compare the resulting pressure and entropy density with the most-recent lattice-QCD calculations at zero baryochemical potential. Finally, we present some exploratory results at finite chemical potential which include the phase diagram of the model, the quark and meson masses, and finally, the thermodynamical pressure.
Comments:
44 pages, 23 figures. Small improvements and more explanations added. Reference list updated. Comparison with recent lattice-QCD results incorporated. Version accepted by the Physical Review C journal
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.07858 [pdf]
PRC(2017)·35 citations
03
[Submitted on 25 Apr 2017]
Reduced transition probabilities for the gamma decay of the 7.8 eV isomer in $^{229}$ Th
Nikolay Minkov · Adriana Pálffy
The reduced magnetic dipole and electric quadrupole transition probabilities for the radiative decay of the $^{229}$ Th 7.8 eV isomer to the ground state are predicted within a detailed nuclear-structure model approach. We show that the presence and decay of this isomer can only be accounted for by the Coriolis mixing emerging from a remarkably fine interplay between the coherent quadrupole-octupole motion of the nuclear core and the single-nucleon motion within a reflection-asymmetric deformed potential. We find that the magnetic dipole transition probability which determines the radiative lifetime of the isomer is considerably smaller than presently estimated. The so-far disregarded electric quadrupole component may have non-negligible contributions to the internal conversion channel. These findings support new directions in the experimental search of the $^{229}$ Th transition frequency for the development of a future nuclear frequency standard.
Comments:
5 pages, 1 figure, supplementary material is available as pdf with the source files, v3 includes small corrections to match the published version, results unchanged
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1704.07919 [pdf]
PRL(2017)·78 citations
04
[Submitted on 26 Apr 2017]
Isovector properties of the nuclear energy density functional from the quark-meson coupling model
E. McRae🇦🇺 · C. Simenel🇦🇺 · E. C. Simpson🇦🇺 · A. W. Thomas🇦🇺
Background: The Skyrme energy density functional is widely used in mean-field calculations of nuclear structure and dynamics. However, its reliance on phenomenology may compromise its isovector properties and its performance for exotic nuclear systems. Purpose: This work investigates the possibility of removing some phenomenology from the density functional by drawing on the high-energy degrees-of-freedom of the quark-meson coupling (QMC) model. The QMC model has microscopically derived isovector properties and far fewer adjustable parameters. Method: The parameters of the Skyrme interaction are fixed using the energy density functional of the QMC model, to give the Skyrme-QMC (SQMC) parameterisation. Results: Hartree-Fock-Bogoliubov calculations of the Sn, Pb and $N = 126$ chains are reported, in which SQMC performs with an accuracy comparable to modern phenomenological functionals. Conclusions: The isovector terms of the energy density functional are significant for the binding energies of neutron-rich nuclei. The isovector dependence of the nuclear spin-orbit interaction must be taken into account for calculations of r-process nucleosynthesis abundances.
Comments:
11 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.07991 [pdf]
PoS(2017)·2 citations
05
[Submitted on 26 Apr 2017]
Bose-Einstein condensation and liquid-gas phase transition in alpha-matter
L. M. Satarov🇩🇪 · M. I. Gorenstein🇩🇪 · A. Motornenko🇩🇪 · V. Vovchenko🇩🇪 · I. N. Mishustin🇩🇪 · H. Stoecker🇩🇪
Systems of Bose particles with both repulsive and attractive interactions are studied using the Skyrme-like mean-field model. The phase diagram of such systems exhibits two special lines in the chemical potential-temperature plane: one line which represents the first-order liquid-gas phase transition with the critical end point, and another line which represents the onset of Bose-Einstein condensation. The calculations are made for strongly-interacting matter composed of alpha particles. The phase diagram of this matter is qualitatively similar to that observed for the atomic He4 liquid. The sensitivity of the results to the model parameters is studied. For weak interaction coupling the critical point is located at the Bose-condensation line.
Comments:
14 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.08039 [pdf]
J.Phys.G(2017)·21 citations
06
[Submitted on 26 Apr 2017]
Relative mass distributions of neutron-rich thermally fissile nuclei within statistical model
Bharat Kumar · M.T. Senthil kannan · M. Balasubramaniam · B. K. Agrawal · S. K. Patra
We study the fission yield of recently predicted thermally fissile neutron-rich uranium and thorium nuclei using statistical model. The level density parameters needed for the study are evaluated from the excitation energies of temperature dependent relativistic mean field formalism. The excitation energy and the level density parameter for a given temperature are employed in the convolution integral method to obtain the probability of the particular fragmentation. As representative case, we present the results for the binary fission yield of 250 U and 254 Th. The relative yields are presented for three different temperatures T = 1, 2 and 3 MeV.
Comments:
Comments are welcome. arXiv admin note: text overlap with arXiv:1612.01667
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.08105 [pdf]
PRC(2017)·7 citations
07
[Submitted on 25 Apr 2017] (cross-list from hep-ph)
Nuclear effects are relevant to the calorimetric reconstruction of neutrino energy
Artur M. Ankowski🇺🇸
As the calorimetric method of neutrino-energy reconstruction is generally considered to be largely insensitive to nuclear effects, its application seems to be an effective way for reducing systematic uncertainties in oscillation experiments. To verify the validity of this opinion, we quantitatively study the sensitivity of the calorimetric energy reconstruction to the effect of final-state interactions in an ideal detector and in a realistic scenario. We find that when particles escaping detection carry away a non-negligible fraction of neutrino energy, the calorimetric reconstruction method becomes sensitive to nuclear effects which, in turn, affects the outcome of the oscillation analysis. These findings suggest that the best strategy for reduction of systematic uncertainties in future neutrino-oscillation studies---such as the Deep Underground Neutrino Experiment---is to increase their sensitivity to particles of low energy. The ambitious precision goals appear also to require an extensive development of theoretical models capable of providing an accurate predictions for exclusive cross sections of well-controlled uncertainties.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1704.07835 [pdf]
8 citations
08
[Submitted on 25 Apr 2017] (cross-list from hep-ph)
Theoretical Perspective on Quarkonia from SPS via RHIC to LHC
Ralf Rapp🇺🇸 · Xiaojian Du🇺🇸
The objective of this paper is to assess the current theoretical understanding of the extensive set of quarkonium observables (for both charmonia and bottomonia) that have been attained in ultrarelativistic heavy-ion collisions over two orders of magnitude in center-of-mass energy. We briefly lay out and compare the currently employed theoretical frameworks and their underlying transport coefficients, and then analyze excitation functions of quarkonium yields to characterize the nature of the varying production mechanisms. We argue that an overall coherent picture of suppression and regeneration mechanisms emerges which enables to deduce insights on the properties of the in-medium QCD force from SPS via RHIC to LHC, and forms a basis for future quantitative studies.
Comments:
8 pages, 10 figures; contribution to proceedings of XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017), Chicago (IL, USA), Feb. 05-11, 2017
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1704.07923 [pdf]
NPA(2017)·36 citations
09
[Submitted on 26 Apr 2017] (cross-list from nucl-ex)
Structure of $^{20}$ Ne states in the resonance $^{16}$ O+ $α$ elastic scattering
D. K. Nauruzbayev · V. Z. Goldberg · A. K. Nurmukhanbetova · M. S. Golovkov · A. Volya · G. V. Rogachev · R. E. Tribble
Background The nuclear structure of the cluster bands in $^{20}$ Ne presents a challenge for different theoretical approaches. It is especially difficult to explain the broad 0 $^{+}$ , 2 $^{+}$ states at 9 MeV excitation energy. Simultaneously, it is important to obtain more reliable experimental data for these levels in order to quantitatively assess the theoretical framework. Purpose To obtain new data on $^{20}$ Ne $α$ cluster structure. Method Thick target inverse kinematics technique was used to study the $^{16}$ O+ $α$ resonance elastic scattering and the data were analyzed using an \textit{R} matrix approach. The $^{20}$ Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model (CNCIM). Results We determined the parameters of the broad resonances in \textsuperscript{20}Ne: 0 $^{+}$ level at 8.77 $\pm$ 0.150 MeV with a width of 750 (+500/-220) keV; 2 $^{+}$ level at 8.75 $\pm$ 0.100 MeV with the width of 695 $\pm$ 120 keV; the width of 9.48 MeV level of 65 $\pm$ 20 keV and showed that 9.19 MeV, 2 $^{+}$ level (if exists) should have width $\leq$ 10 keV. The detailed comparison of the theoretical CNCIM predictions with the experimental data on cluster states was made. Conclusions Our experimental results by the TTIK method generally confirm the adopted data on $α$ cluster levels in $^{20}$ Ne. The CNCIM gives a good description of the $^{20}$ Ne positive parity states up to an excitation energy of $\sim$ 7 MeV, predicting reasonably well the excitation energy of the states and their cluster and single particle properties. At higher excitations, the qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Accelerator Physics (physics.acc-ph)
arXiv:
1704.08154 [pdf]
PRC(2017)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE