Nuclear Theory·nucl-th

Monday·March 11, 2019

10 papers—6 primary·4 cross-listed

01
[Submitted on 7 Mar 2019]
Density-dependent NN-interaction from subleading chiral 3N-forces: Long-range terms
N. Kaiser · B. Singh
We derive from the subleading contributions to the chiral three-nucleon force (long-range terms, published in Phys.\,Rev.\,C\,77, 064004 (2008)) a density-dependent two-nucleon interaction $V_{med}$ in isospin-symmetric, spin-saturated nuclear matter. Following the division of the pertinent 3N-diagrams into two-pion exchange topology, two-pion-one-pion exchange topology and ring topology, we evaluate for these all self-closings and concatenations of nucleon-lines to an in-medium loop. The momentum and $k_{f}$ -dependent potentials associated with the isospin operators ( $1$ and $τ_{1} \cdot τ_{2}$ ) and five independent spin-structures are expressed in terms of functions, which are either given in closed analytical form or require at most one numerical integration. In the same way we treat the $2 π$ -exchange 3N-force up to fourth order. Our results for $V_{med}$ are most helpful to implement the long-range subleading chiral 3N-forces into nuclear many-body calculations.
Comments:
19 pages, 1 figure, 1 table, typo in eq.(82) corrected
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1903.03183 [pdf]
PRC(2019)·24 citations
02
[Submitted on 8 Mar 2019]
Update of a Multi-Phase Transport Model with Modern Parton Distribution Functions and Nuclear Shadowing
Chao Zhang🇨🇳 · Liang Zheng🇨🇳 · Feng Liu🇨🇳 · Shusu Shi🇨🇳 · Zi-Wei Lin🇨🇳
A multi-phase transport (AMPT) model has been successful in explaining a wide range of observables in relativistic heavy ion collisions. In this work, we implement a modern set of free proton parton distribution functions and an impact parameter-dependent nuclear shadowing in the AMPT model. After refitting the parameters of the two-component initial condition model to the experimental data on $pp$ and $p p ˉ$ total and inelastic cross sections from $s \sim$ 4 GeV to 13 TeV, we study particle productions in $pp$ and $AA$ collisions. We show that the updated AMPT model with string melting can reasonably describe the overall particle yields and transverse momentum spectra for both $pp$ and $AA$ collisions at RHIC and LHC energies after we introduce a nuclear scaling of the minijet transverse momentum cutoff for $AA$ collisions at LHC energies that is motivated by the color glass condensate. Since heavy flavor and high- $p_{T}$ particles are produced by perturbative-QCD processes and thus directly depend on parton distribution functions of nuclei, the updated AMPT model is expected to provide a more reliable description of these observables.
Comments:
10 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1903.03292 [pdf]
PRC(2019)·31 citations
03
[Submitted on 8 Mar 2019]
Suddenly shortened half-lives beyond $^{78}$ Ni: $N = 50$ magic number and high-energy non-unique first-forbidden transitions
Kenichi Yoshida
$β$ -decay rates play a decisive role in understanding the nucleosynthesis of heavy elements and are governed by microscopic nuclear-structure information. A sudden shortening of the half-lives of Ni isotopes beyond $N = 50$ was observed at the RIKEN-RIBF. This is considered due to the persistence of the neutron magic number $N = 50$ in the very neutron-rich Ni isotopes. By systematically studying the $β$ -decay rates and strength distributions in the neutron-rich Ni isotopes around $N = 50$ , I try to understand the microscopic mechanism for the observed sudden shortening of the half-lives. The $β$ -strength distributions in the neutron-rich nuclei are described in the framework of nuclear density-functional theory. I employ the Skyrme energy-density functionals (EDF) in the Hartree-Fock-Bogoliubov calculation for the ground states and in the proton-neutron Quasiparticle Random-Phase Approximation (pnQRPA) for the transitions. Not only the allowed but the first-forbidden (FF) transitions are considered. The experimentally observed sudden shortening of the half-lives beyond $N = 50$ is reproduced well by the calculations employing the Skyrme SkM* and SLy4 functionals. The sudden shortening of the half-lives is due to the shell gap at $N = 50$ and cooperatively with the high-energy transitions to the low-lying $0^{-}$ and $1^{-}$ states in the daughter nuclei. The onset of FF transitions pointed out around $N = 82$ and 126 is preserved in the lower-mass nuclei around $N = 50$ . This study suggests that needed is a microscopic calculation where the shell structure in neutron-rich nuclei and its associated effects on the FF transitions are selfconsistenly taken into account for predicting $β$ -decay rates of exotic nuclei in unknown region.
Comments:
8 pages, 7 figures and 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1903.03310 [pdf]
PRC(2019)·13 citations
04
[Submitted on 8 Mar 2019]
Mapping neutron star data to the equation of state using the deep neural network
Yuki Fujimoto🇯🇵 · Kenji Fukushima🇯🇵 · Koichi Murase🇯🇵
The densest state of matter in the universe is uniquely realized inside central cores of the neutron star. While first-principles evaluation of the equation of state of such matter remains as one of the longstanding problems in nuclear theory, evaluation in light of neutron star phenomenology is feasible. Here we show results from a novel theoretical technique to utilize deep neural network with supervised learning. We input up-to-date observational data from neutron star X-ray radiations into the trained neural network and estimate a relation between the pressure and the mass density. Our results are consistent with extrapolation from the conventional nuclear models and the experimental bound on the tidal deformability inferred from gravitational wave observation.
Comments:
14 pages, 5 figures; updates in Figs. 2 and 3
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1903.03400 [pdf]
PRD(2020)·143 citations
05
[Submitted on 8 Mar 2019]
Multi-chiral facets in symmetry restored states: Five chiral doublets candidates in even-even nucleus $^{136}$ Nd
Y. K. Wang · F. Q. Chen · P. W. Zhao · S. Q. Zhang · J. Meng
A triaxial projected shell model including configurations with more than four quasiparticles in the configuration space is developed, and applied to investigate the recently reported five chiral doublets candidates in a single even-even nucleus $^{136}$ Nd. The energy spectra and transition probability ratios $B (M 1) / B (E 2)$ are reproduced satisfactorily. The configuration mixing along the rotational bands is studied by analyzing the intrinsic composition of the eigenfunctions. The chiral geometry of these nearly degenerate bands is examined by the \textit{K plot} and the \textit{azimuthal plot}, and the evolution from the chiral vibration to the static chirality with spin is clearly demonstrated for four pairs of partner bands. From the features in the \textit{azimuthal plot}, it is difficult to interpret the other candidate as chiral partners.
Comments:
4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1903.03497 [pdf]
PRC(2019)·24 citations
06
[Submitted on 8 Mar 2019]
Neutrino pion-production on a nucleon
Fred Myhrer🇺🇸
Heavy baryon chiral perturbation theory ( $χ$ PT), where the $Δ$ resonance is included, is used in order to examine the axial charged-current component of the weak interaction process at low neutrino energies. At leading chiral order the Adler theorems, derived using PCAC, are satisfied. At next-to-leading chiral order this effective field theory goes beyond these theorems. I will show that $χ$ PT generates deviation from the PCAC predictions, which means that some neutrino-nucleon models that are used in evaluating neutrino nucleus scattering amplitudes, might need modifications.
Comments:
7 pages, 1 figure, Talk at the 9th International Workshop on Chiral Dynamics,Sept. 17-21, 2018, Duke University, Durham, NC, USA
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1903.03542 [pdf]
PoS(2019)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Density-dependent NN-interaction from subleading chiral 3N-forces: Long-range terms

Update of a Multi-Phase Transport Model with Modern Parton Distribution Functions and Nuclear Shadowing

Suddenly shortened half-lives beyond 78Ni: N=50 magic number and high-energy non-unique first-forbidden transitions

Mapping neutron star data to the equation of state using the deep neural network

Multi-chiral facets in symmetry restored states: Five chiral doublets candidates in even-even nucleus 136Nd

Neutrino pion-production on a nucleon

Affiliations

Suddenly shortened half-lives beyond $^{78}$ Ni: $N = 50$ magic number and high-energy non-unique first-forbidden transitions

Multi-chiral facets in symmetry restored states: Five chiral doublets candidates in even-even nucleus $^{136}$ Nd