Nuclear Theory·nucl-th

Tuesday·October 16, 2018

17 papers—14 primary·3 cross-listed

01
[Submitted on 12 Oct 2018]
Physics of nuclei: Key role of an emergent symmetry
T. Dytrych · K. D. Launey · J. P. Draayer · D. Rowe · J. Wood · G. Rosensteel · C. Bahri · D. Langr · R. B. Baker
Exact symmetry and symmetry-breaking phenomena play a key role in providing a better understanding of the physics of many-particle systems, from quarks and atomic nuclei, to molecules and galaxies. In atomic nuclei, exact and dominant symmetries such as rotational invariance, parity, and charge independence have been clearly established. However, even when these symmetries are taken into account, the structure of nuclei remains illusive and only partially understood, with no additional symmetries immediately evident from the underlying nucleon-nucleon interaction. Here, we show through ab initio large-scale nuclear structure calculations that the special nature of the strong nuclear force determines additional highly regular patterns in nuclei that can be tied to an emergent approximate symmetry. We find that this symmetry is remarkably ubiquitous, regardless of its particular strong interaction heritage, and mathematically tracks with a symplectic group. Specifically, we show for light to intermediate-mass nuclei that the structure of a nucleus, along with its low-energy excitations, respects symplectic symmetry at about 70-80% level, unveiling the predominance of only a few equilibrium shapes, deformed or not, with associated vibrations and rotations. This establishes the symplectic symmetry as a remarkably good symmetry of the strong nuclear force, in the low-energy regime. This may have important implications to studies in astrophysics and neutrino physics that rely on nuclear structure information, especially where experimental measurements are incomplete or not available. A very important practical advantage is that this new symmetry can be utilized to dramatically reduce computational resources required in ab initio large-scale nuclear structure modeling. This, in turn, can be used to pioneer predictions, e.g., for short-lived isotopes along various nucleosynthesis pathways.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.05757 [pdf]
PRL(2020)·113 citations
02
[Submitted on 13 Oct 2018]
Partial dynamical symmetry and the vibrational structure of Cd isotopes
A. Leviatan🇮🇱 · N. Gavrielov🇮🇱 · J.E. Garcia-Ramos🇪🇸 · P. Van Isacker🇫🇷
The recently reported deviations of selected non-yrast states in $^{110}$ Cd from the expected spherical-vibrator behaviour, is addressed by means of an Hamiltonian with U(5) partial dynamical symmetry. The latter preserves the U(5) symmetry in a segment of the spectrum and breaks it in other states. The effect of intruder states is treated in the framework of the interacting boson model with configuration mixing.
Comments:
3 pages, 2 figures, talk at 16th Int. Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16), September 18-22, 2017, Shanghai Jiao Tong University, China
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.05917 [pdf]
EPJ Web Conf.(2018)·3 citations
03
[Submitted on 14 Oct 2018]
$B_{c}$ mesons and their properties on the light front
Shuo Tang🇺🇸 · Yang Li🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸
We investigate the unequal mass relativistic bound state system, the $B_{c}$ mesons, in a light-front Hamiltonian formalism. We adopt an effective Hamiltonian based on soft-wall light-front holography, together with a longitudinal confinement that was first introduced for heavy quarkonium. We also include the one gluon-exchange interaction with a running coupling, which produces the spin structure. We present the mass spectrum and light-front wave functions. We also use the light-front wave functions to calculate decay constants, charge and momentum densities, as well as distribution amplitudes. The results are compared with experiments and other theoretical approaches, all of which are in reasonable agreement.
Comments:
11 pages, 6 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1810.05971 [pdf]
PRD(2018)·67 citations
04
[Submitted on 14 Oct 2018]
Fusion Cross Section of $T (d, n)^{4} He$ and $^{3} He (d, p)^{4} He$ Reactions by Four Parameters Formula
T. Koohrokhi · A. M. Izadpanah · S. K. Hosseini
Fusion cross sections of light nuclei are calculated by a complex potential and taking into account of conservation of angular momentum and parity. The nuclear potential is assumed to be as simple as a spherical complex square well with a rigid core. Then, the nuclear phase shift is extracted from continuity condition of inverse of the logarithmic derivative of the wave functions as a complex quantity. The quantum tunneling probability and cross section are obtained via real and complex components of nuclear phase shift. The obtained results for the two most important light nuclei reactions, $T (d, n)^{4} He$ , $^{3} He (d, p)^{4} He$ are compared with other theoretical formulas and experimental data. Despite that the theory is simplified as much as possible and the complexities and details of nuclear interactions has been ignored, excellent agreements with experimental data are achieved.
Comments:
Journal of Fusion Energy (2016)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.05975 [pdf]
2 citations
05
[Submitted on 14 Oct 2018]
Simple description of the temperature dependencies of the width of fission-fragment mass yield in 197Au and 209Bi at intermediate energies
V. Yu. Denisov · O. A. Belyanovska · V. P. Khomenkov · I. Yu. Sedykh · K. M. Sukhyy
Simple approach is used to a description of the experimental data for the widths of fission fragment mass yields in 197Au and 209Bi at low and intermediate energies. This approach based on both the expression for the temperature dependence of the width of fission fragment mass yield and the mass of the most probable fragment. The expression for the width of fission fragment mass yield depends on the mass of the most probable fragment, the surface terms of the energy level density parameter, the temperature and the stiffness parameter of the potential related to mass-asymmetric degree of freedom. It is shown that the contribution of the surface term of the energy level density parameter into the width is important for description of the experimental data in wide range of energies.
Comments:
5 pages, 2 figures, to be published in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.06000 [pdf]
CPC(2019)·2 citations
06
[Submitted on 14 Oct 2018]
Electromagnetic currents of the pion-nucleon system
T. Skawronski🇦🇺 · B. Blankleider🇦🇺 · A. N. Kvinikhidze🇬🇪
Pion photoproduction amplitudes are calculated from a set of equations that have been derived by coupling an external photon to all places in a dressed pion-nucleon vertex. The calculation is consistent with gauge invariance, charge conservation, unitarity and covariance. To provide input to the photoproduction amplitude, a photon-nucleon vertex is calculated from a set of equations derived by complete attachment of photons to a dressed nucleon propagator. We check the accuracy of this vertex by extracting its nucleon electromagnetic form factors.
Comments:
18 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.06035 [pdf]
PRC(2019)·1 citation
07
[Submitted on 14 Oct 2018]
A pseudo-conformal structure in dense baryonic matter
Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
We clarify and extend further the idea developed in \cite{PKLMR,MLPR} that baryonic matter at high density has an emergent "pseudo-conformal symmetry." It is argued that as baryonic density exceeds $n ≃ n_{1/2} ≳ 2 n_{0}$ , a topology change mimicking the baryon-quark continuity takes place at $n_{1/2}$ . In terms of skyrmions, this corresponds to the transition from skyrmions to half-skyrmions and impacts on the equation of state of dense baryonic matter. The emergence in medium at $n_{1/2}$ of parity-doublet symmetry -- which is invisible in QCD in matter-free vacuum -- plays the crucial role. The consequence of the topology change is that massive compact stars carry the "pseudo-conformal sound velocity" $v_{s}^{2} / c^{2} \approx 1/3$ at $n \gsim n_{1/2}$ signaling a precursor to precocious emergence of scale symmetry as well as {a} local symmetry hidden in QCD in the matter-free vacuum. A highly significant prediction of this work is that the topology change density from normal matter to half-skyrmion matter, up-to-date inaccessible either by QCD proper or by terrestrial experiments, could possibly be pinned down within the range $2 < n_{1/2} / n_{0} < 4$ , commensurate with the range expected for a continuous hadrons-to-quarks/gluons transition.
Comments:
Version published in Phys. Rev. D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1810.06062 [pdf]
PRD(2019)·26 citations
08
[Submitted on 14 Oct 2018]
Systematic investigation of the high- $K$ isomers and the high-spin rotational bands in the neutron rich Nd and Sm isotopes by a particle-number conserving method
Zhen-Hua Zhang
The rotational properties of the neutron rich Nd and Sm isotopes with mass number $A \approx 150$ are systematically investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. The 2-quasiparticle states in even-even Nd and Sm isotopes with excitation energies lower than 2.5~MeV are systematically calculated. The available data can be well reproduced and some possible 2 and 4-quasiparticle isomers are also suggested for future experiments. The experimentally observed rotational frequency variations of moments of inertia for the even-even and odd- $A$ nuclei are reproduced very well by the calculations. The effects of high-order deformation $ε_{6}$ on the 2-quasiparticle excitation energies and moments of inertia of the ground state bands in even-even Nd and Sm isotopes are analyzed in detail. By analyzing the occupation probability $n_{μ}$ of each cranked Nilsson orbitals near the Fermi surface and the contribution of each major shell to the angular momentum alignments, the alignment mechanism in these nuclei is understood clearly.
Comments:
25 pages, 8 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.06086 [pdf]
PRC(2018)·13 citations
09
[Submitted on 14 Oct 2018]
What do we learn about vector interactions from GW170817?
Veronica Dexheimer🇺🇸 · Rosana de Oliveira Gomes🇩🇪 · Stefan Schramm🇩🇪 · Helena Pais🇵🇹
We analyze the role played by vector-isovector meson interaction in dense matter present in the interior of neutron stars in the light of new measurements made during the double neutron-star merger GW170817. These concern measurements of tidal deformability from gravitational waves and electromagnetic observations. Our study includes three different equations of state that contain different physical assumptions and matter compositions, namely the NL3 family, MBF, and CMF models. Other related quantities/relations analyzed are the neutron matter pressure, symmetry energy slope, stellar masses and radii, and Urca process threshold for stellar cooling.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1810.06109 [pdf]
J.Phys.G(2019)·82 citations
10
[Submitted on 14 Oct 2018]
Composite-particle decay widths by the generator coordinate method
G.F. Bertsch · W. Younes
We study the feasibility of applying the Generator Coordinate Method (GCM) of self-consistent mean-field theory to calculate decay widths of composite particles to composite-particle final states. The main question is how well the GCM can approximate continuum wave functions in the decay channels. The analysis is straightforward under the assumption that the GCM wave functions are separable into internal and Gaussian center-of-mass wave functions. Two methods are examined for calculating decays widths. In one method, the density of final states is computed entirely in the GCM framework. In the other method, it is determined by matching the GCM wave function to an asymptotic scattering wave function. Both methods are applied to a numerical example and are found to agree within their determined uncertainties.
Comments:
9 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); physics.atm-clus (physics.atm-clus)
arXiv:
1810.06124 [pdf]
Annals Phys.(2019)·21 citations
11
[Submitted on 15 Oct 2018]
Uncertainty quantification due to optical potentials in models for (d,p) reactions
G. B. King · A. E. Lovell · F. M. Nunes
Recent work has studied the uncertainty in predictions for A(d,p)B reactions using the distorted-wave Born approximation (DWBA), coming from the parameterization of the effective dA interactions [Lovell et al., Phys. Rev. C 95, 024611]. There are different levels of sophistication in theories for one-nucleon transfer reactions, including the adiabatic wave approximation (ADWA) which takes deuteron breakup into account to all orders. In this work, we quantify the uncertainties associated with the ADWA method that come from the parameterization of the NA interactions, and compare ADWA with DWBA. We use nucleon elastic-scattering data on a wide variety of targets to constrain the optical potential input to the ADWA theory. Pulling from the $χ^{2}$ -distribution, we obtain 95% confidence plots for the elastic distributions. From the resulting parameters, we predict 95% confidence bands for the (d,p) transfer cross sections. Results obtained with the uncorrelated $χ^{2}$ are compared to those using the correlated $χ^{2}$ of Lovell et al. We also repeat the DWBA calculations for the same reactions for comparison purposes. We find that NA elastic scattering data provides a significant constraint to the interactions, and, when the uncertainties are propagated to the transfer reactions using ADWA, predictions are consistent with the transfer data. The angular distributions for ADWA differ from those predicted by DWBA, particularly at small angles. Confidence bands obtained using the uncorrelated $χ^{2}$ -function are unrealistically narrow and become much wider when the correlated $χ^{2}$ -function is considered. For most cases, the uncertainty bands obtained in ADWA are narrower than DWBA, when using elastic data of similar quality and range. However, given the large uncertainties predicted from the correlated $χ^{2}$ -function, the transfer data cannot discriminate between these two methods.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.06129 [pdf]
PRC(2018)·27 citations
12
[Submitted on 15 Oct 2018]
Recent theoretical results for electromagnetically induced ultraperipheral reactions of heavy ions
Antoni Szczurek🇵🇱
We briefly review our works on ultraperipheral heavy ion collisions. We discuss both $γ γ$ and rescattering of hadronic photon fluctuation induced by one nucleus in the collision partner. Production of one and two leptonic and pionic and $p p ˉ$ pairs is discussed as an example of photon-photon processes. The production of single vector mesons ( $ρ^{0}$ or $J / ψ$ ) is an example of the second category. The double-scattering mechanisms of two $ρ^{0}$ meson production is discussed in addition.
Comments:
10 pages, 15 figures, invited talk at WPCF2018 conference
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1810.06249 [pdf]
2 citations
13
[Submitted on 15 Oct 2018]
Ab initio Folding Potentials for Nucleon-Nucleus Scattering based on NCSM One-Body Densities
M. Burrows · Ch. Elster · S.P. Weppner · K.D. Launey · P. Maris · A. Nogga · G. Popa
Calculating microscopic optical potentials for elastic nucleon-nucleus scattering has already led to large body of work in the past. For folding first-order calculations the nucleon-nucleon (NN) interaction and the one-body density of the nucleus were taken as input to rigorous calculations in a spectator expansion of the multiple scattering series. Based on the Watson expansion of the multiple scattering series we employ a nonlocal translationally invariant nuclear density derived from a chiral next-to-next-to-leading order (NNLO) and the very same interaction for consistent full-folding calculation of the effective (optical) potential for nucleon-nucleus scattering for light nuclei. We calculate scattering observables, such as total, reaction, and differential cross sections as well as the analyzing power and the spin-rotation parameter, for elastic scattering of protons and neutrons from $^{4}$ He, $^{6}$ He, $^{12}$ C, and $^{16}$ O, in the energy regime between 100 and 200~MeV projectile kinetic energy, and compare to available data. Our calculations show that the effective nucleon-nucleus potential obtained from the first-order term in the spectator expansion of the multiple scattering expansion describes experiments very well to about 60 degrees in the center-of-mass frame, which coincides roughly with the validity of the NNLO chiral interaction used to calculate both the NN amplitudes and the one-body nuclear density.
Comments:
10 pages, 14 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.06442 [pdf]
PRC(2019)·51 citations
14
[Submitted on 15 Oct 2018]
Identifying structures in the continuum: Application to $^{16}$ Be
J. Casal · J. Gómez-Camacho
The population and decay of two-nucleon resonances offer exciting new opportunities to explore dripline phenomena. The understanding of these systems requires a solid description of the three-body (core+N+N) continuum. The identification of a state with resonant character from the background of non-resonant continuum states in the same energy range poses a theoretical challenge. It is the purpose of this work to establish a robust theoretical framework to identify and characterize three-body resonances in a discrete basis. A resonance operator is proposed, which describes the sensitivity to changes in the potential. Resonances are then identified from the lowest eigenstates of the resonance operator. The operator is diagonalized in a basis of Hamiltonian pseudostates, built within the hyperspherical harmonics formalism using the analytical THO basis. The energy and width of the resonance are determined from its time dependence. The method is applied to 16Be in a 14Be+n+n model. An effective core+n potential, fitted to the available information on the subsystem 15Be, is employed. The 0+ ground state resonance of 16Be presents a strong dineutron configuration, which favors the picture of a correlated two-neutron emission. Fitting the three body interaction to the experimental two-neutron separation energy |S2n|=1.35(10) MeV, the computed width is Gamma(0+)=0.16 MeV. From the same Hamiltonian, a 2+ resonance is also predicted with E_r(2+)=2.42 MeV and Gamma(2+)=0.40 MeV. The dineutron configuration and the computed 0+ width are consistent with previous R-matrix calculations for the true three-body continuum. The extracted values of the resonance energy and width converge with the size of the pseudostate basis and are robust under changes in the basis parameters. This supports the reliability of the method in describing the properties of unbound core+N+N systems in a discrete basis.
Comments:
11 pages, 14 figures. Accepted as PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.06447 [pdf]
PRC(2019)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE