Nuclear Theory·nucl-th

Thursday·April 18, 2019

11 papers—5 primary·6 cross-listed

01
[Submitted on 17 Apr 2019]
Systematic study of proton radioactivity based on Gamow--like model with a screened electrostatic barrier
Jiu-Long Chen · Xiao-Hua Li · Jun-Hao Cheng · Jun-Gang Deng · Xi-Jun Wu
In the present work we systematically study the half--lives of proton radioactivity for $51 \leq Z \leq 83$ nuclei based on the Gamow--like model with a screened electrostatic barrier. In this model there are two parameters while considering the screened electrostatic effect of Coulomb potential with the Hulthen potential i.e. the effective nuclear radius parameter r_0 and the screening parameter a. The calculated results can well reproduce the experimental data. In addition, we extend this model to predict the proton radioactivity half--lives of 16 nuclei in the same region within a factor of 2.94, whose proton radioactivity are energetically allowed or observed but not yet quantified. Meanwhile, studying on the proton radioactivity half-life by a type of universal decay law has been done. The results indicate that the calculated half--lives are linearly dependent on Coulomb parameter with the same orbital angular momentum.
Comments:
12 pages, 5 figures, accepted by Journal of Physics G: Nuclear and Particle Physics
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.08243 [pdf]
J.Phys.G(2019)·24 citations
02
[Submitted on 17 Apr 2019]
Initial conditions of bulk matter in ultrarelativistic nuclear collisions
J. Scott Moreland🇺🇸
Dynamical models based on relativistic fluid dynamics provide a powerful tool to extract the properties of the strongly-coupled quark-gluon plasma (QGP) produced by ultrarelativistic nuclear collisions. The largest source of uncertainty in these model-to-data extractions is the choice of theoretical initial conditions (ICs) used to model the distribution of energy or entropy at the hydrodynamic starting time. Descriptions of the ICs are generally improved through iterative cycles of testing and refinement. Individual models are compared to experimental data; the worst models are discarded and best models retained. Consequently, successful traits (assumptions) are passed on to subsequent generations of the theoretical landscape. This bottom-up approach correspondingly describes a form of theoretical trial and error, where each trial proposes an ab initio solution to the problem at hand. A natural complement to this strategy, is to employ a top-down or data-driven approach which is able to reverse engineer properties of the ICs from the constraints imposed by the experimental data. In this dissertation, I motivate and develop a parametric IC model based on a family of functions known as the generalized means. The ansatz closely mimics the variability of ab initio calculations and serves as a reasonable parametric form for exploring QGP energy and entropy deposition assuming imperfect knowledge of the complex physical processes which lead to its creation. With the parametric model in hand, I explore broad implications of the proposed ansatz using recently adapted Bayesian methods to simultaneously constrain properties of the ICs and QGP medium using experimental data from the Large Hadron Collider. These analyses show that the ICs are highly constrained by available measurements and provide evidence of a unified hydrodynamic description of small and large nuclear collision systems.
Comments:
Ph.D. dissertation; 250 pages, 91 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.08290 [pdf]
9 citations
03
[Submitted on 17 Apr 2019]
Individual dipole toroidal states: main features and search in (e,e') reaction
V.O. Nesterenko · A. Repko · J. Kvasil · P.-G. Reinhard
Individual low-energy E1 toroidal and compressional states (TS and CS) produced by the convective nuclear current $j_{c}$ were recently predicted for $^{24}$ Mg in the framework of quasiparticle random-phase-approximation (QRPA) with Skyrme forces. In the present QRPA study with Skyrme parametrization SLy6, we explore in more detail properties of these states (toroidal and compressional responses, current distributions, and transitions probabilities $B (E 1 K, 0^{+} 0 \to 1^{-} K), B (E 3 K, 0^{+} 0 \to 3^{-} K)$ , $B (M 2 K, 0^{+} 0 \to 2^{-} K)$ with $K =$ 0 and 1) and analyze the possibility to discriminate and identify TS in inelastic electron scattering to back angles. The interplay of the convective $j_{c}$ and magnetization $j_{m}$ nuclear currents is thoroughly scrutinized. A two-step scheme for identification of TS in $(e, e^{'})$ reaction is proposed. The key element of the scheme is the strong interference of the orbital and spin contributions, resulting in specific features of E1 and M2 transversal form factors.
Comments:
10 pages, 9 figures. The previous version of the paper was crucially revised and enlarged in both i) description on main features and ii) proposals for (e,e') reaction. Submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.08302 [pdf]
PRC(2019)·11 citations
04
[Submitted on 17 Apr 2019]
Hadron-Deuteron Correlations and Production of Light Nuclei in Relativistic Heavy-Ion Collisions
Stanislaw Mrowczynski🇵🇱 · Patrycja Slon🇵🇱
The production of light nuclei in relativistic heavy-ion collisions is well described by both the thermal model, where light nuclei are in equilibrium with all other hadron species present in a fireball, and by the coalescence model, where light nuclei are formed due to final state interactions after the fireball decays. A method is proposed to falsify one of the models. We suggest to measure a hadron-deuteron correlation function which carries information about the source of the deuterons and allows one to determine whether a deuteron is directly emitted from the fireball or if it is formed afterwards. The $K^{-} - D$ and $p - D$ correlation functions are computed to illustrate the statement.
Comments:
16 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1904.08320 [pdf]
Acta Phys.Polon.B(2020)·52 citations
05
[Submitted on 17 Apr 2019]
Interface effects of strange quark matter
Cheng-Jun Xia🇨🇳
The interface effects play important roles for the properties of strange quark matter (SQM) and the related physical processes. We show several examples on the implications of interface effects for both stable and unstable SQM. Based on an equivparticle model and adopting mean-field approximation (MFA), the surface tension and curvature term of SQM can be obtained, which are increasing monotonically with the density of SQM at zero external pressure. For a parameter set constrained according to the 2 $M_{⊙}$ strange star, we find the surface tension is $\sim$ 2.4 MeV/fm $^{2}$ , while it is larger for other cases.
Comments:
To appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy, Jan. 3-7, Xiamen, China
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
1904.08347 [pdf]
AIP Conf.Proc.(2019)·6 citations
06
[Submitted on 16 Apr 2019] (cross-list from hep-ph)
Spontaneous generation of spin current from the vacuum by strong electric fields
Xu-Guang Huang🇨🇳 · Mamoru Matsuo🇨🇳 · Hidetoshi Taya🇨🇳
We discuss spontaneous spin current generation from the vacuum by strong electric fields as a result of interplay between the Schwinger mechanism and a spin-orbit coupling. By considering a homogeneous slow strong electric field superimposed by a fast weak transverse electric field, we explicitly evaluate the vacuum expectation value of a spin current (the Bargmann-Wigner spin current) by numerically solving the Dirac equation. We show that a non-vanishing spin current polarized in the direction perpendicular to the electric fields flows mostly in the longitudinal direction. We also find that a relativistic effect due to the helicity conservation affects direction/polarization of spin current.
Comments:
v2: 16 pages, 5 figures; discussions and references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); cond-mat.mtrl-sci (cond-mat.mtrl-sci); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1904.07593 [pdf]
PTEP(2019)·12 citations
07
[Submitted on 16 Apr 2019] (cross-list from astro-ph.HE)
Improved photomeson model for interactions of cosmic ray nuclei
Leonel Morejon🇩🇪 · Anatoli Fedynitch🇩🇪 · Denise Boncioli🇩🇪 · Daniel Biehl🇩🇪 · Walter Winter🇩🇪
Photon-hadronic interactions are important for the sources and the transport of Ultra-High Energy Cosmic Rays (UHECRs). Current state-of-the-art cosmic ray transport simulations handle nuclear disintegration at energies of the Giant Dipole Resonance at a more sophisticated level, as well as the photohadronic interactions of nucleons in the high-energy regime above the pion production threshold. However, the interactions of nuclei above the pion production threshold are commonly modeled by treating the nucleus as a superposition of free nucleons -- ignoring the effect of the nuclear medium. We construct an improved, inclusive model for the photomeson regime for nuclei with $A \leq 56$ by employing more accurate, data-driven parametrizations of the interaction cross section, the fragmentation of the primary nucleus and the inclusive pion production cross section that directly affects the production of astrophysical neutrinos. We apply our results to two multi-messenger scenarios (Tidal Disruption Events and Gamma-Ray Bursts) in which photonuclear interactions in the photomeson regime are the dominant cooling process for the highest energy cosmic rays. While we find moderate changes to the mass composition of UHECRs, the astrophysical neutrino fluxes exhibit a significant (factor of a few) reduction compared to the naïve superposition of free nucleons for sources of UHECR nuclei with a populated cascade. The numerical code implementing the model has been made publicly available, which facilitates the integration of our results in similar frameworks.
Comments:
Accepted for publication in JCAP. Main changes from previous version: 1.Corrected treatment of the pion production at high energies. 2.Added two new figures comparing the model to experimental data. Software tools available at https://github.com/mohller/AstroPhoMes/ Cite the code using the DOI 10.5281/zenodo.2600177
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1904.07999 [pdf]
JCAP(2019)·48 citations
08
[Submitted on 16 Apr 2019] (cross-list from hep-ph)
Nucleon resonance contributions to unpolarised inclusive electron scattering
A. N. Hiller Blin🇩🇪 · V. Mokeev🇺🇸 · M. Albaladejo🇺🇸 · C. Fernández-Ramírez🇲🇽 · V. Mathieu🇺🇸 · A. Pilloni🇮🇹 · A.Szczepaniak🇺🇸 · V. D. Burkert🇺🇸 · V. V. Chesnokov🇷🇺 · A. A. Golubenko🇷🇺 · M. Vanderhaeghen🇩🇪
The first CLAS12 experiments will provide high-precision data on inclusive electron scattering observables at a photon virtuality $Q^{2}$ ranging from 0.05 GeV $^{2}$ to 12 GeV $^{2}$ and center-of-mass energies $W$ up to 4 GeV. In view of this endeavour, we present the modeling of the resonant contributions to the inclusive electron scattering observables. As input, we use the existing CLAS electrocoupling results obtained from exclusive meson electroproduction data off protons, and evaluate for the first time the resonant contributions based on the experimental results on the nucleon resonance electroexcitation. The uncertainties are given by the data and duly propagated through a Monte Carlo approach. In this way, we obtain estimates for the resonant contributions, important for insight into the nucleon parton distributions in the resonance region and for the studies of quark-hadron duality.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.08016 [pdf]
PRC(2019)·46 citations
09
[Submitted on 17 Apr 2019] (cross-list from hep-ph)
Spin-dependent dynamically assisted Schwinger mechanism
Xu-Guang Huang🇨🇳 · Hidetoshi Taya🇨🇳
We study electron and positron pair production from the vacuum by a strong slow electric field superimposed by a weak fast electric field pointing in an arbitrary direction as a perturbation (the dynamically assisted Schwinger mechanism). An analytical formula for the production number is derived on the basis of the perturbation theory in the Furry picture. The formula is found to be in good agreement with non-perturbative results obtained by numerically solving the Dirac equation if the perturbation is sufficiently weak and/or is not very slow. We also find analytically/numerically that the Schwinger mechanism becomes spin-dependent if the perturbation has a transverse component with respect to the strong electric field. The number difference between spin up and down particles is strongly suppressed by an exponential of the critical field strength if the frequency of the perturbation is small, while it is only weakly suppressed by powers of the critical field strength if the frequency is large enough. We also find that the spin-imbalance exhibits non-trivial oscillating behaviors in terms of the frequency of the perturbation, the azimuthal angle, and the momentum of produced particles.
Comments:
23 pages, 11 figures; v2: results for the total production number are added, the validity of the perturbative approach is discussed in more detail, figures are improved, typos are corrected, version to be published in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Plasma Physics (physics.plasm-ph); Quantum Physics (quant-ph)
arXiv:
1904.08200 [pdf]
PRD(2019)·27 citations
10
[Submitted on 17 Apr 2019] (cross-list from hep-ph)
Angular mode expansion of the Boltzmann equation in the small-angle approximation
Jean-Paul Blaizot🇫🇷 · Naoto Tanji🇮🇹
We use an expansion in angular mode functions in order to solve the Boltzmann equation for a gluon plasma undergoing longitudinal expansion. By comparing with the exact solution obtained numerically by other means we show that the expansion in mode functions converges rapidly for all cases of practical interest, and represents a substantial gain in numerical effort as compared to more standard methods. We contrast the cases of a non expanding plasma and of longitudinally expanding plasmas, and follow in both cases the evolutions towards thermalization. In the latter case, we observe that, although the spherical mode function appears to be well reproduced after some time by a local equilibrium distribution function depending on slowly varying temperature and chemical potential, thereby suggesting thermalization of the system, the longitudinal and transverse pressures take more time to equilibrate. This is because the expansion hinders the relaxation of the first angular mode function. This feature was also observed in a simpler context where the Boltzmann equation is solved in terms of special moments within the relaxation time approximation, and attributed there to the particular coupling between the first two moments of the distribution function. The present analysis confirms this observation in a more realistic setting.
Comments:
23 pages, 16 figures, version published in Nuclear Physics A
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.08244 [pdf]
NPA(2019)·4 citations
11
[Submitted on 17 Apr 2019] (cross-list from hep-ph)
The analytic structure of thermodynamic systems with repulsive interactions
Kirill Taradiy🇺🇦 · Anton Motornenko🇩🇪 · Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Horst Stoecker🇩🇪
Thermodynamic properties of systems with repulsive interactions, are considered in the grand canonical ensemble. The analytic structure of the excluded-volume model in the complex plane of the system chemical potential (fugacity) is elaborated, based on the fact that the pressure function can be given in terms of the Lambert W-function. Even though the excluded volume model has no phase transitions at real values of the chemical potential, it does exhibit a branch cut singularity in the complex plane, thus limiting the convergence range of the Taylor expansion in the chemical potential. Close similarities to analytic properties of the other models with repulsive interactions, such as a cluster expansion model, the mean-field model, and the ideal Fermi gas model, are pointed out. As an example, repulsive baryonic interactions in a hadron gas, with a focus on the fugacity/virial and Taylor expansion methods used in lattice QCD, are presented. The asymptotic behavior of the Fourier expansion coefficients in these various models suggests that the singular part of net baryonic density can to leading order be universally expressed in terms of polylogarithms.
Comments:
11 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1904.08259 [pdf]
PRC(2019)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE