Nuclear Theory·nucl-th

Monday·April 24, 2017

9 papers—6 primary·3 cross-listed

01
[Submitted on 20 Apr 2017]
Standardized Cumulants of Flow Harmonic Fluctuations
Navid Abbasi🇮🇷 · Davood Allahbakhshi🇮🇷 · Ali Davody🇮🇷 · Seyed Farid Taghavi🇮🇷
The distribution of flow harmonics in heavy ion experiment can be characterized by standardized cumulants. We first model the ellipticity and power parameters of the elliptic-power distribution by employing MC-Glauber model. Then we use the elliptic-power distribution together with the hydrodynamic linear response approximation to study the two dimensional standardized cumulants of elliptic and triangular flow ( $v_{2}$ and $v_{3}$ ) distribution. For the second harmonic, it turns out that finding two dimensional cumulants in terms of $2 q$ -particle correlation functions $c_{2} {2 q}$ is limited to the skewness. We also show that $c_{3} {2}$ , $c_{3} {4}$ , and $c_{3} {6}$ , are related to the second, fourth, and sixth standardized cumulants of the $v_{3}$ distribution, respectively. The cumulant $c_{n} {2 q}$ can be also written in terms of $v_{n} {2 q}$ . Specifically, $- (v_{3} {4} / v_{3} {2})^{4}$ turns out to be the kurtosis of the $v_{3}$ event-by-event fluctuation distribution. We introduce a new parametrization for the distribution $p (v_{3})$ with $v_{3} {2}$ , kurtosis and sixth-order standardized cumulant being its free parameters. Compared to the Gaussian distribution, it indicates a more accurate fit with experimental results. Finally, we compare the kurtosis obtained from simulation with that of extracted from experimental data for the $v_{3}$ distribution.
Comments:
16 pages; 9 figures; v2: published version; The statistic of hydrodynamic simulation is increased for centralities below 40%; Hydrodynamic simulation results are removed from Fig. 2 and 3; Fig. 7 is added; A plot corresponds to the $p_{T}$ dependence of $Γ_{2}$ is added to Fig. 9;
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.06295 [pdf]
PRC(2018)·21 citations
02
[Submitted on 20 Apr 2017]
Assessing theoretical uncertainties in fission barriers of superheavy nuclei
S. E. Agbemava · A. V. Afanasjev · D. Ray · P. Ring
Theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way for a set of state-of-the-art covariant energy density functionals which represent major classes of the functionals used in covariant density functional theory. They differ in basic model assumptions and fitting protocols. Both systematic and statistical uncertainties have been quantified where the former turn out to be larger. Systematic uncertainties are substantial in superheavy elements and their behavior as a function of proton and neutron numbers contains a large random component. The benchmarking of the functionals to the experimental data on fission barriers in the actinides allows to reduce the systematic theoretical uncertainties for the inner fission barriers of unknown superheavy elements. However, even then they on average increase on moving away from the region where benchmarking has been performed. In addition, a comparison with the results of non-relativistic approaches is performed in order to define full systematic theoretical uncertainties over the state-of-the-art models. Even for the models benchmarked in the actinides, the difference in the inner fission barrier height of some superheavy elements reaches $5 - 6$ MeV. This uncertainty in the fission barrier heights will translate into huge (many tens of the orders of magnitude) uncertainties in the spontaneous fission half-lives.
Comments:
18 pages, 12 figures, submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.06334 [pdf]
PRC(2017)·58 citations
03
[Submitted on 21 Apr 2017]
Analytical and numerical assessment of accuracy of the approximated nuclear symmetry energy in the Hartree-Fock theory
Y. Tsukioka · H. Nakada
The nuclear symmetry energy is defined by the second derivative of the energy per nucleon with respect to the proton-neutron asymmetry, and is sometimes approximated by the energy difference between the neutron matter and the symmetric matter. Accuracy of this approximation is assessed analytically and numerically, within the Hartree-Fock theory using effective interactions. By decomposing the nuclear-matter energy, the relative error of each term is expressed analytically; it is constant or is a single-variable function determined by the function type. The full errors are evaluated for several effective interactions, by inserting values of the parameters. Although the errors stay within $10%$ up to twice of the normal density irrespective of the interactions, at higher densities accuracy of the approximation significantly depends on the interactions.
Comments:
14 pages, 3 figures (each has 2 panels)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.06407 [pdf]
PTEP(2017)·4 citations
04
[Submitted on 21 Apr 2017]
Imprint of Nucleon Radius on the Slowly Rotating Neutron Star Properties
Suparti · A. Sulaksono · T. Mart
We have studied the effect of free space nucleon radius on the nuclear matter and slowly rotating neutron star properties within a relativistic mean field model with the inclusion of omega-rho mixing nonlinear term. We use the same density dependent radius as in our previous work. However, in the present work we utilize the parameter sets with more proper symmetric nuclear matter (SNM) predictions for a number of different nucleon radii. To this end, the isoscalar parameters in each parameter set and the cutoff parameter $β$ are adjusted by fitting the corresponding SNM properties at sub-saturation density to the prediction of IUFSU parameter set. We have obtained that the assumption of composite nucleons with free space radius $r \leq 0.83$ fm is still compatible with the currently acceptable nuclear matter (NM) properties beyond the saturation density. We have also found that the effect of free space nucleon radius could be imprinted in the radius, moment of inertia, and crust properties of the slowly rotating neutron star.
Comments:
23 pages, 9 figures, Phys. Rev. C (accepted)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.06545 [pdf]
0 citations
05
[Submitted on 21 Apr 2017]
Refining mass formulas for astrophysical applications: a Bayesian neural network approach
Raditya Utama · Jorge Piekarewicz
Exotic nuclei, particularly those near the driplines, are at the core of one of the fundamental questions driving nuclear structure and astrophysics today: what are the limits of nuclear binding? Exotic nuclei play a critical role in both informing theoretical models as well as in our understanding of the origin of the heavy elements. Our purpose is to refine existing mass models through the training of an artificial neural network that will mitigate the large model discrepancies far away from stability. The basic paradigm of our two-pronged approach is an existing mass model that captures as much as possible of the underlying physics followed by the implementation of a Bayesian Neural Network (BNN) refinement to account for the missing physics. Bayesian inference is employed to determine the parameters of the neural network so that model predictions may be accompanied by theoretical uncertainties. Despite the undeniable quality of the mass models adopted in this work, we observe a significant improvement (of about 40%) after the BNN refinement is implemented. Indeed, in the specific case of the Duflo-Zuker mass formula, we find that the rms deviation relative to experiment is reduced from rms =0.503MeV to rms=0.286 MeV. These newly refined mass tables are used to map the neutron drip lines (or rather "drip bands") and to study a few critical r-process nuclei. The BNN approach is highly successful in refining the predictions of existing mass models. In particular, the large discrepancy displayed by the original "bare" models in regions where experimental data is unavailable is considerably quenched after the BNN refinement. This lends credence to our approach and has motivated us to publish refined mass tables that we trust will be helpful for future astrophysical applications.
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1704.06632 [pdf]
PRC(2017)·93 citations
06
[Submitted on 21 Apr 2017]
Hydrodynamic modeling of heavy-ion collisions
Li Yan🇨🇦
This contribution presents a theoretical overview of hydrodynamic modelling of heavy-ion collisions, with highlights on some recent developments. In particular, the formulation of anisotropic hydrodynamics, the role of hydrodynamic fluctuations, and the non-linear coupling of flow coefficients will be discussed.
Comments:
Proceedings of XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1704.06643 [pdf]
NPA(2017)·4 citations
07
[Submitted on 21 Apr 2017] (cross-list from nucl-ex)
Spectroscopic factor and proton formation probability for the d3/2 proton emitter 151mLu
F. Wang🇨🇳 · B. H. Sun🇨🇳 · Z. Liu🇨🇳 · R. D. Page🇬🇧 · C. Qi🇸🇪 · C. Scholey🇫🇮 · S. F. Ashley🇬🇧 · L. Bianco🇬🇧 · I. J. Cullen🇬🇧 · I. G. Darby🇺🇸 · S. Eeckhaudt🇫🇮 · A. B. Garnsworthy🇨🇦 and 33 other authors
The quenching of the experimental spectroscopic factor for proton emission from the short-lived $d_{3/2}$ isomeric state in $^{151 m}$ Lu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) $μ$ s, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of $^{151 m}$ Lu.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1704.06394 [pdf]
PLB(2017)·18 citations
08
[Submitted on 21 Apr 2017] (cross-list from hep-ph)
Crossover-model approach to QCD phase diagram, equation of state and susceptibilities in the 2+1 and 2+1+1 flavor systems
Akihisa Miyahara🇯🇵 · Masahiro Ishii🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵
We construct a simple model for describing the hadron-quark crossover transition by using lattice QCD (LQCD) data in the 2+1 flavor system, and draw the phase diagram in the 2+1 and 2+1+1 flavor systems through analyses of the equation of state (EoS) and the susceptibilities. In the present hadron-quark crossover (HQC) model is successful in reproducing LQCD data on the EoS and the flavor susceptibilities.We define the hadron-quark transition temperature. For the 2+1 flavor system, the transition line thus obtained is almost identical in planes that are created by temperature and the chemical potential for the baryon-number(B), the isospin(I), the hypercharge(Y), when the chemical potentials are smaller than 250 MeV. This BIY approximate equivalence persists also in the 2+1+1 flavor system. We plot the phase diagram also in planes that are created by temperature and the chemical potential for u,d,s quark number in order to investigate flavor dependence of transition lines. In the 2+1+1 flavor system, c quark does not affect the 2+1 flavor subsystem composed of u, d, s. The flavor off-diagonal susceptibilities are good indicators to see how hadrons survive as T increases, since the independent quark model hardly contributes to them.
Comments:
14 pages, 35figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1704.06432 [pdf]
Int.J.Mod.Phys.A(2017)·6 citations
09
[Submitted on 21 Apr 2017] (cross-list from hep-ph)
Magnetic field influence on the early time dynamics of heavy-ion collisions
Moritz Greif🇩🇪 · Carsten Greiner🇩🇪 · Zhe Xu🇨🇳
In high energy heavy-ion collisions the magnetic field is very strong right after the nuclei penetrate each other and a non-equilibrium system of quarks and gluons builds up. Even though quarks might not be very abundant initially, their dynamics must necessarily be influenced by the Lorentz force. Employing the 3+1d partonic cascade BAMPS we show that the circular Larmor movement of the quarks leads to a strong positive anisotropic flow of quarks at very soft transverse momenta. We explore the regions where the effect is visible, and explicitly show how collisions damp the effect. As a possible application we look at photon production from the flowing non-equilibrium medium.
Comments:
8 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.06505 [pdf]
PRC(2017)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE