Nuclear Theory·nucl-th

Tuesday·May 25, 2021

10 papers—5 primary·5 cross-listed

01
[Submitted on 22 May 2021]
Nuclear masses in extended kernel ridge regression with odd-even effects
X. H. Wu · L. H. Guo · P. W. Zhao
The kernel ridge regression (KRR) approach is extended to include the odd-even effects in nuclear mass predictions by remodulating the kernel function without introducing new weight parameters and inputs in the training network. By taking the WS4 mass model as an example, the mass for each nucleus in the nuclear chart is predicted with the extended KRR network, which is trained with the mass model residuals, i.e., deviations between experimental and calculated masses, of other nuclei with known masses. The resultant root-mean-square mass deviation from the available experimental data for the 2353 nuclei with $Z \geq 8$ and $N \geq 8$ can be reduced to 128 keV, which provides the most precise mass model from machine learning approaches so far. Moreover, the extended KRR approach can avoid the risk of worsening the mass predictions for nuclei at large extrapolation distances, and meanwhile, it provides a smooth extrapolation behavior with respect to the odd and even extrapolation distances.
Comments:
6 pages,3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2105.10634 [pdf]
PLB(2021)·57 citations
02
[Submitted on 23 May 2021]
Impact of NICER's Radius Measurement of PSR J0740+6620 on Nuclear Symmetry Energy at Suprasaturation Densities
Nai-Bo Zhang · Bao-An Li
By directly inverting several neutron star observables in the three-dimensional parameter space for the Equation of State of super-dense neutron-rich nuclear matter, we show that the lower radius limit for PSR J0740+6620 of mass $2.08 \pm 0.07 M_{⊙}$ from Neutron Star Interior Composition Explorer (NICER)'s very recent observation sets a much tighter lower boundary than previously known for nuclear symmetry energy in the density range of $(1.0 \sim 3.0)$ times the saturation density $ρ_{0}$ of nuclear matter. The super-soft symmetry energy leading to the formation of proton polarons in this density region of neutron stars is clearly disfavoured by the first radius measurement for the most massive neutron star observed reliably so far.
Comments:
New calculations/discussions/references added. The Astrophysical Journal in press
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2105.11031 [pdf]
ApJ(2021)·53 citations
03
[Submitted on 24 May 2021]
Astrophysical S factor and rate of $^{7} Be (p, γ)^{8} B$ direct capture reaction in a potential model
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov · L.D. Blokhintsev
The astrophysical $^{7} Be (p, γ)^{8} B$ direct capture process is studied in the framework of a two-body single-channel model with potentials of the Gaussian form. A modified potential is constructed to reproduce the new experimental value of the $S$ -wave scattering length and the known astrophysical $S$ factor at the Gamow energy, extracted from the solar neutrino flux. The resulting potential is consistent with the theory developed by Baye [Phys. Rev. C {\bf 62} (2000) 065803] according to which the $S$ -wave scattering length and the astrophysical $S$ factor at zero energy divided by the square of ANC are related. The obtained results for the astrophysical $S$ factor at intermediate energies are in good agreement with the two data sets of Hammache {\it et al.} [Phys. Rev. Lett. {\bf 86}, 3985 (2001); {\it ibid.} {\bf 80}, 928 (1998)]. Linear extrapolation to zero energy yields $S_{17} (0) \approx (20.5 \pm 0.5) eV b$ , consistent with the Solar Fusion II estimate. The calculated reaction rates are substantially lower than the results of the NACRE II collaboration.
Comments:
16 pages, 5 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2105.11091 [pdf]
PRC(2021)·9 citations
04
[Submitted on 24 May 2021]
Systematic shell-model study of Rn isotopes with $A =$ 207 to 216 and isomeric states
Bharti Bhoy · Praveen C. Srivastava
We present systematic large-scale shell-model calculations for Rn isotopes with $A =$ 207 to 216. For the $^{207 - 212}$ Rn isotopes, we perform calculations with KHH7B interaction, while for $^{213 - 216}$ Rn isotopes with KHPE and KHH7B interactions. The calculated energies and electromagnetic properties are compared with the available experimental data and predicted where experimental data are not available. We also suggest spins and parities of several unconfirmed states available from the recent experimental data. Comprehensive study of several isomeric states from the calculated shell-model configurations and half-lives is also reported.
Comments:
Accepted in Journal of Physics G: Nuclear and Particle Physics (2021)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2105.11096 [pdf]
J.Phys.G(2021)·11 citations
05
[Submitted on 24 May 2021]
A Realistic Approach to the $Ξ N N$ Bound-State Problem based on Faddeev Equation
K. Miyagawa🇯🇵 · M. Kohno🇯🇵
The Faddeev equations for the $Ξ N N$ bound-state problem are solved where the three $S$ = $- 2$ baryon-baryon interactions of Jülich-Bonn-München chiral EFT, HAL QCD and Nijmegen ESC08c are used. The $T$ -matrix $T_{Ξ N, Ξ N}$ obtained within the original $ΛΛ$ - $Ξ N$ - $ΣΣ$ $/$ $Ξ N$ - $ΛΣ$ - $ΣΣ$ coupled-channel framework is employed as an input to the equations. We found no bound state for Jülich-Bonn-München chiral EFT and HAL QCD but ESC08c generates a bound state with the total isospin and spin-parity $(T, J^{π}) = (1/2, 3/ 2^{+})$ where the decays into $ΛΛ N$ are suppressed.
Comments:
to appear in the proceedings of APFB2020
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.11258 [pdf]
Few Body Syst.(2021)·10 citations
06
[Submitted on 21 May 2021] (cross-list from hep-ph)
Delineating chiral separation effect in two-color dense QCD
Daiki Suenaga🇯🇵 · Toru Kojo🇨🇳
We study the chiral separation effect (CSE) in two-color and two-flavor QCD (QC $_{2}$ D) to delineate quasiparticle pictures in dense matter from low to high temperatures. Both massless and massive quarks are discussed. We particularly focus on the high density domain where diquarks form a color singlet condensate with the electric charge $1/3$ . The condensate breaks baryon number and $U (1)_{A}$ axial symmetry, and induces the electromagnetic Meissner effects. Within a quark quasiparticle picture, we compute the chiral separation conductivity at one-loop. We have checked that Nambu-Goldstone modes, which should appear in the improved vertices as required by the Ward-Takahashi identities, do not contribute to the chiral separation conductivity due to their longitudinal natures. In the static limit, the destructive interferences in the particle-hole channel, as in usual Meissner effects, suppress the conductivity (in chiral limit, to $1/3$ of the normal phase's). This locally breaks the universality of the CSE coefficients, provided quasiparticle pictures are valid in the bulk matter.
Comments:
12 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2105.10538 [pdf]
PRD(2021)·9 citations
07
[Submitted on 21 May 2021] (cross-list from nucl-ex)
Isotope Shifts of Radium Monofluoride Molecules
S.M. Udrescu🇺🇸 · A.J. Brinson🇺🇸 · R.F. Garcia Ruiz🇺🇸 · K. Gaul🇩🇪 · R. Berger🇩🇪 · J. Billowes🇬🇧 · C.L. Binnersley🇬🇧 · M.L. Bissell🇬🇧 · A.A. Breier🇩🇪 · K. Chrysalidis🇨🇭 · T.E. Cocolios🇧🇪 · B.S. Cooper🇬🇧 and 16 other authors
Isotope shifts of $^{223 - 226, 228}$ Ra $^{19}$ F were measured for different vibrational levels in the electronic transition $A^{2} Π_{1/2} \leftarrow X^{2} Σ^{+}$ . The observed isotope shifts demonstrate the particularly high sensitivity of radium monofluoride to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. Ab initio quantum chemical calculations are in excellent agreement with experimental observations. These results highlight some of the unique opportunities that short-lived molecules could offer in nuclear structure and in fundamental symmetry studies.
Comments:
The paper was accepted for publication as a Letter in Physical Review Letters
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2105.10549 [pdf]
PRL(2021)·44 citations
08
[Submitted on 24 May 2021] (cross-list from cond-mat.quant-gas)
Complex Langevin study for polarons in an attractively interacting one-dimensional two-component Fermi gas
Takahiro M. Doi🇯🇵 · Hiroyuki Tajima🇯🇵 · Shoichiro Tsutsui🇯🇵
We investigate a polaronic excitation in a one-dimensional spin-1/2 Fermi gas with contact attractive interactions, using the complex Langevin method, which is a promising approach to evade a possible sign problem in quantum Monte Carlo simulations. We found that the complex Langevin method works correctly in a wide range of temperature, interaction strength, and population imbalance. The Fermi polaron energy extracted from the two-point imaginary Green's function is not sensitive to the temperature and the impurity concentration in the parameter region we considered. Our results show a good agreement with the solution of the thermodynamic Bethe ansatz at zero temperature.
Comments:
18 pages, 5 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2105.11072 [pdf]
PRResearch(2021)·7 citations
09
[Submitted on 24 May 2021] (cross-list from math-ph)
Transport Synthetic Acceleration for the Solution of the One-Speed Nonclassical Spectral S $_{N}$ Equations in Slab Geometry
Japan K. Patel · Leonardo R. C. Moraes · Richard Vasques · Ricardo C. Barros
The nonclassical transport equation models particle transport processes in which the particle flux does not decrease as an exponential function of the particle's free-path. Recently, a spectral approach was developed to generate nonclassical spectral S $_{N}$ equations, which can be numerically solved in a deterministic fashion using classical numerical techniques. This paper introduces a transport synthetic acceleration procedure to speed up the iteration scheme for the solution of the monoenergetic slab-geometry nonclassical spectral S $_{N}$ equations. We present numerical results that confirm the benefit of the acceleration procedure for this class of problems.
Comments:
14 pages, 2 figures
Subjects:
Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
2105.11083 [pdf]
J.Comput.Appl.Math.(2022)·0 citations
10
[Submitted on 24 May 2021] (cross-list from hep-ph)
Centrality and transverse momentum dependence of hadrons in Pb+Pb collisions at LHC
Lilin Zhu🇨🇳 · Hua Zheng🇨🇳 · Rudolph C. Hwa🇺🇸
The transverse momentum spectra of seven identified hadrons produced in Pb+Pb collisions at $s_{N N} = 2.76$ and 5.02 TeV at the CERN Large Hadron Collider (LHC) have been investigated in the framework of the recombination model (RM). Soft, semihard and hard partons all play important roles in our model and are uniformly treated for all hadrons produced.The investigation has been extended to non-central collisions and the parameters controlling the momentum degradation of semihard partons have been tuned. Our study shows good agreement between theoretical results and experimental data. To be able to provide a coherent explanation for the production of all identified hadrons ( $π$ , p, K, $Λ$ , $ϕ$ , $Ξ$ , $Ω$ ) for transverse momenta as high as 14 GeV/c (for $π$ , p and K), and for all centralities, is an unprecedented achievement that supports the RM as a sensible model to combine various mechanisms of parton production with a universal scheme of hadronization.
Comments:
9 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2105.11161 [pdf]
PRC(2021)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE