Nuclear Theory·nucl-th

Wednesday·May 8, 2019

8 papers—7 primary·1 cross-listed

01
[Submitted on 7 May 2019]
Charmonium-nucleon interactions from 2+1 flavor lattice QCD
Takuya Sugiura🇯🇵 · Yoichi Ikeda🇯🇵 · Noriyoshi Ishii🇯🇵
The charmonium-nucleon interaction is studied by the time-dependent HAL QCD method. We use a larger lattice volume and the relativistic heavy quark action for charm quark to obtain less systematic errors than those in our previous study. As a result, the sizable J/ $ψ$ N hyperfine splitting is observed, indicating that the spin-spin interaction is important to understand this system quantitatively. No J/ $ψ$ N or $η_{c}$ N bound state is observed below the thresholds as in the previous results.
Comments:
7pages, 5figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
arXiv:
1905.02336 [pdf]
PoS(2019)·15 citations
02
[Submitted on 7 May 2019]
Systematic study of $α$ decay half-lives based on Gamow--like model with a screened electrostatic barrier
Jun-Hao Cheng · Jiu-Long Chen · Jun-Gang Deng · Xi-Jun Wu · Xiao-Hua Li · Peng-Cheng Chu
In the present work we systematically study $α$ decay half-lives of $Z > 51$ nuclei using the modified Gamow-like model which includes the effects of the centrifugal potential and electrostatic shielding. For the case of even-even nuclei, this model contains two adjustable parameters: the parameter $a$ related to the screened electrostatic barrier and the radius constant $r_{0}$ , while for the case of odd-odd and odd-A nuclei, it is added a new parameter i.e. hindrance factor $h$ which is used to describe the effect of an odd-proton and/or an odd-neutron. Our calculations can well reproduce the experimental data. In addition, we use this modified Gamow-like model to predict the $α$ -decay half-lives of seven even-even nuclei with $Z = 120$ and some un-synthesized nuclei on their $α$ decay chains.
Comments:
30 pages, 6 figures. This paper has been accepted by Nuclear Physics, Section A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1905.02344 [pdf]
NPA(2019)·19 citations
03
[Submitted on 7 May 2019]
Scattering phase shifts and mixing angles for an arbitrary number of coupled channels on the lattice
Lukas Bovermann🇩🇪 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪 · Dean Lee🇺🇸
We present a lattice method for determining scattering phase shifts and mixing angles for the case of an arbitrary number of coupled channels. Previous nuclear lattice effective field theory simulations were restricted to mixing of up to two partial waves for scattering of two spin- $1/2$ particles, which is insufficient for analyzing nucleon-nucleus or nucleus-nucleus scattering processes. In the proposed method, the phase shifts and mixing angles are extracted from the radial wave functions obtained by projecting the three-dimensional lattice Hamiltonian onto the partial wave basis. We use a spherical wall potential as a boundary condition along with a channel-mixing auxiliary potential to construct the full-rank $S$ matrix. Our method can be applied to particles with any spin, but we focus here on scattering of two spin- $1$ bosons involving up to four coupled channels. For a considered test potential, the phase shifts and mixing angles extracted on the lattice are shown to agree with the ones calculated by solving the Schrödinger equation in the continuum.
Comments:
14 pages, 9 figures, 1 table, corresponds to the published version in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
arXiv:
1905.02492 [pdf]
PRC(2019)·9 citations
04
[Submitted on 6 May 2019]
Gross, intermediate and fine structure of nuclear giant resonances: Evidence for doorway states
Peter von Neumann-Cosel (1) · Vladimir Yu. Ponomarev (1) · Achim Richter (1) · Jochen Wambach (1,2) ((1) Institut für Kernphysik, Technische Universität Darmstadt, Germany, (2) European Centre for Theoretical Studies in Nuclear Physics and related Areas (ECT*) and Fondazione Bruno Kessler, Villazzano, Italy)
We review the phenomenon of fine structure of nuclear giant resonances and its relation to different resonance decay mechanisms. Wavelet analysis of the experimental spectra provides quantitative information on the fine structure in terms of characteristic scales. A comparable analysis of resonance strength distributions from microscopic approaches incorporating one or several of the resonance decay mechanisms allows conclusions on the source of the fine structure. For the isoscalar giant quadrupole resonance (ISGQR), spreading through the first step of the doorway mechanism, i.e.\ coupling between one particle-one hole ( $1 p 1 h$ ) and two particle-two hole ( $2 p 2 h$ ) states is identified as the relevant mechanism. In heavy nuclei it is dominated by coupling to low-lying surface vibrations, while in lighter nuclei stochastic coupling becomes increasingly important. The fine structure observed for the isovector giant dipole resonance (IVGDR) arises mainly from the fragmentation of the $1 p 1 h$ strength (Landau damping), although some indications for the relevance of the spreading width are also found.
Comments:
15 pages, 16 figures. Submitted to Eur. Phys. J A, special issue "Giant, pygmy, pairing resonances and related topics"
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1905.02579 [pdf]
EPJA(2019)·16 citations
05
[Submitted on 6 May 2019]
Universal scaling of meson and baryon spectra in p-Pb collisions at 5.02 TeV
N. Liu🇨🇳 · X.L. Du🇨🇳 · L.Y. Qiao🇨🇳 · G.R. Che🇨🇳 · W.C. Zhang🇨🇳
We systematically investigate the scaling property of mesons (pions and kaons) and baryons (protons, $Λ$ , $Ξ$ and $Ω$ ) transverse momentum ( $p_{T}$ ) spectra at different centrality classes (0-5 $%$ , 5-10 $%$ , 10-20 $%$ , 20-40 $%$ , 40-60 $%$ , 60-80 $%$ and 80-100 $%$ ) in proton-lead collisions with center of mass energy per nucleon pair 5.02 TeV. In the low $p_{T}$ region with $p_{T} \leq$ 3.9 (3.1, 2.5, 2.7, 2.4 and 2.8) GeV/c, a universal scaling independent of the centrality is observed in the pion (kaon, proton, $Λ$ , $Ξ$ and $Ω$ ) spectra when a dilatation, $p_{T} \to p_{T} / K$ , is applied. Here $K$ is a scaling parameter depending on the centrality class. We find that the rates at which ln $K$ changes with the logarithmic value of the average value of the number of participating nucleons, ln $⟨ N_{part} ⟩$ , are stronger for baryons than those for mesons. In the high $p_{T}$ region, there is a deviation from the scaling. The more peripheral the collisions are, the more obvious the violation of the scaling is. In the framework of the colour string percolation (CSP) model, we show that mesons and baryons are generated from the decay of clusters formed by strings overlapping in the transverse plane with the same size dispersion but with different mean size. The mean size of clusters for baryons is smaller than that of mesons. For the same hadrons at different centrality classes, the mean size of clusters decreases with the increase of centrality. The fragmentation functions for cluster decay are different for different hadrons, while they are universal for the same hadrons at different centrality classes. The universal scaling of the meson and baryon spectra in the low $p_{T}$ region can be quantitatively understood with the CSP model at the same time.
Comments:
17 pages, 8 figs.,6 tables. Accepted by International Journal of Modern Physics E. arXiv admin note: text overlap with arXiv:1805.02300
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1905.02581 [pdf]
IJMPE(2019)·2 citations
06
[Submitted on 6 May 2019]
Insights on Skyrme parameters from GW170817
C.Y. Tsang🇺🇸 · M.B. Tsang🇺🇸 · Pawel Danielewicz🇺🇸 · W.G. Lynch🇺🇸 · F.J. Fattoyev🇺🇸
The binary neutron-star merger event, GW170817, has cast a new light on nuclear physics research. Using a neutron-star model that includes a crust equation of state (EoS), we calculate the properties of a 1.4 solar-mass neutron star. The model incorporates more than 200 Skyrme energy density functionals, which describe nuclear matter properties, in the outer liquid core region of the neutron star. We find a power-law relation between the neutron-star tidal deformability, $Λ$ , and the neutron-star radius, R. Without an explicit crust EoS, the model predicts smaller R and the difference becomes significant for stars with large radii. To connect the neutron star properties with nuclear matter properties, we confront the predicted values for $Λ$ , against the Taylor expansion coefficients of the Skyrme interactions. There is no pronounced correlation between Skyrme parameters in symmetric nuclear matter and neutron star properties. However, we find the strongest correlation between $Λ$ and $K_{sy m}$ , the curvature of the density dependence of the symmetry energy at saturation density. At twice the saturation density, our calculations show a strong correlation between $Λ$ and total pressure providing guidance to laboratory nucleus-nucleus collision experiments.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.02601 [pdf]
PLB(2019)·68 citations
07
[Submitted on 7 May 2019]
Cross sections at sub-Coulomb energies: full optical model vs.\ barrier transmission for $^{40}$ Ca + $α$
Peter Mohr
Cross sections for $^{40}$ Ca + $α$ at low energies have been calculated from two different models and three different $α$ -nucleus potentials. The first model determines the cross sections from the barrier transmission in a real nuclear potential. Second, cross sections are derived within the optical model using a complex nuclear potential. The excitation functions from barrier transmission are smooth whereas the excitation functions from the optical model show a significant sensitivity to the chosen imaginary potential. Cross sections far below the Coulomb barrier are lower from barrier transmission than from the optical model. This difference is explained by additional absorption in the tail of the imaginary part of the potential in the optical model. At higher energies the calculations from the two models and all $α$ -nucleus potentials converge. Finally, in contradiction to another recent study where a double-folding potential failed in a WKB calculation, the applicability of double-folding potentials for $^{40}$ Ca + $α$ at low energies is clearly confirmed in the present analysis for the simple barrier transmission model and for the full optical model calculation.
Comments:
17 pages, 3 figures, accepted for publication in Int. J. Mod. Phys. E
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.02634 [pdf]
IJMPE(2019)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Charmonium-nucleon interactions from 2+1 flavor lattice QCD

Systematic study of α decay half-lives based on Gamow--like model with a screened electrostatic barrier

Scattering phase shifts and mixing angles for an arbitrary number of coupled channels on the lattice

Gross, intermediate and fine structure of nuclear giant resonances: Evidence for doorway states

Universal scaling of meson and baryon spectra in p-Pb collisions at 5.02 TeV

Insights on Skyrme parameters from GW170817

Cross sections at sub-Coulomb energies: full optical model vs.\ barrier transmission for 40Ca + α

Affiliations

Systematic study of $α$ decay half-lives based on Gamow--like model with a screened electrostatic barrier

Cross sections at sub-Coulomb energies: full optical model vs.\ barrier transmission for $^{40}$ Ca + $α$